An unofficial collaborator or IM (both from German inoffizieller Mitarbeiter) or, euphemistically, informal collaborator (informeller Mitarbeiter) was an informant in the German Democratic Republic (East Germany) who delivered private information to the Ministry for State Security (MfS / Stasi). At the end of the East German government, there was a network of around 189,000 informants, working at every level of society.
Before 1968 the term "Secret Informer" ("Geheimer Informator") was used.
The network of secret informers, commonly known in German sources by the initials IM, was one of the most important instruments of repression and also one of the most critical pillars of power supporting the one party dictatorship that ran the country.
The terms "Informal Collaborator" "Inoffizieller Mitarbeiter" and, before 1968, "Secret Informer" ("Geheimer Informator") were terms chosen carefully by the Stasi in order to distance their operations from the police vocabulary used under the previous regime, and, in particular, to avoid association with the older term used for an informant, "V-Mann" ("Vertrauensmann)"".
During the course of German reunification the Stasi archives were opened up: the identities of numerous IMs came to light, which opened the way for several human tragedies. At the same time many friendships, partnerships and marriages broke apart after previously concealed spying activities became known to both parties.
Since the changes of 1989/90, IM and the other terms here have sometimes also been used for informers who worked for Intelligence organisations other than the Stasi.
The Stasi network of Informal Collaborators (IMs) covered all sections of the population in the Democratic Republic. The network provided crucial support to the country's elaborate surveillance system, and it made possible the monitoring of groups to which an identifiable Stasi officer could never have gained more direct access. There were IMs in many dissident groups and organisations, notably in artistic and church circles, so that the state was informed in particular detail about individuals defined in the official Stasi jargon as "enemy-negative persons" ("feindlich-negativer Personen")
During its lifetime the Stasi employed around 624,000 Informal collaborators. IM numbers rose most steeply at times of societal crises, such as the aftermath of the 1953 uprising and the construction of the Berlin Wall (which began, with the official closing of the border surrounding West Berlin, in August 1961). They fell back a little in the mid-1960s for the initial phase of the period of reduced east-west tensions between the two Germanys associated with the time in office, first as Foreign Minister and then as Chancellor, of Willy Brandt, before climbing steeply through the early 1970s to peak at a little above 200,000 during the mid-1970s. The gentle decline in the overall number of the Informal collaborators for several years in the later 1970s is associated with new guidelines, intended to increase their professionalism. By the end of 1988 the number had declined to 173,081.
The numbers challengedEdit
A younger researcher on the subject, East Berlin born historian Ilko-Sascha Kowalczuk, questioned this figure in 2013, but without providing any similarly careful estimate of his own as to the number of IMs in 1988/89. There is a suggestion that Müller-Enbergs' higher figure includes people who operated under more than one cover name and in more than one IM category, leading to some double counting in his revised figure. Another consideration is that the Stasi data include many people who never actually reported anything to them. The Stasi themselves archived the records of nearly 10,000 inactive IMs in 1987. In 1988 the Stasi were using, internally, the much lower figure of 110,000. Kowalczuk also questioned the extrapolated figure for IMs based outside the country.
A challenge challengedEdit
Kowalczuks own figures, appearing in his book "Stasi konkret" (2013), have not gone unchallenged, with criticisms that his conclusions are empirically unconvincing, that his logic contains grave errors, and that his statistical approach is flawed. Assertions by Kowalczuk in the press appearing to state that the number of IMs was only half that previously accepted are inaccurate because they take no account of the massive broadening of information gathering activity by the Stasi that was a feature of the final years of the German Democratic Republic, and left almost every second citizen thinking himself a surveillance victim. Kowalczuk's employers at the Federal Commission for Stasi Records (BStU) in effect later distanced themselves from his figures, and an (in other respects unimportant) application by the Federal (national) government later in 2013 also implied rejection of Kowalczuk's position.
189,000 Informal collaborators (IM)s in 1989Edit
The BStU continues to accept the Müller-Enbergs figure of 189,000 IMs, including more than 10,000 in the category "Gesellschaftlicher Mitarbeiter Sicherheit" (see "Categories of Informal Collaborator" below). The BStU believes that between 3,000 and 3,500 of these Stasi IMs were operating in West Germany and West Berlin, and they reckon that 1,550 of these were working for the HVA (effectively the "foreign" division of the intelligence service). It is in any event clear, as the BStU has repeatedly pointed out, that the term "Informal collaborator" ( "Inoffizieller Mitarbeiter" / "Informeller Mitarbeiter"’ /"IM") was not always precisely defined, and that very careful investigation is needed in order to prove any individual case on order that the individual responsibility, or where appropriate the guilt, of any one person may be determined. The importance of treating each case individually is as important in serving the public just as for research purposes. Some have nevertheless claimed that there are essential differences between the two. The debate about numbers and the ensuing clarifications provided by the BStU have in the end provided some reassurance about the soundness of the 189,000 figure.
Other Stasi informantsEdit
There is also evidence that the Stasi had significant numbers of informants in addition to the IMs. In the residential areas the Stasi relied on "Information people" ("Auskunftspersonen " / AKPs), for information on neighbours. These were informants who in most circumstances would not themselves have been listed as IMs, and whose information gathering would mostly have been controlled by senior Stasi officers. They would have sought to conceal the true basis for their "curiosity", as representing, for instance, the local council, the military or the tax office in order to get their target-interlocutors talking. Details of these AKPs, including the extent of their willingness to talk, were documented in the Stasi files. Sample based analysis of these Stasi records in Rostock and Saalfeld shows that approximately 18% and 5.9% of the populations, respectively, were assessed as AKPs who were, for the most part, ready to talk. That means that in these places the IMs were outnumbered many times over by these "Information people" ( AKPs). In Karl-Marx-Stadt (the name of which has since reverted to Chemnitz) the Stasi had contacts with people they defined as "good people" ("gute Menschen"), people ready to be helpful to them. In business and workplaces, state institutions and social organisations, the Stasi worked with "official" partners. Usually these were people in key positions, which normally meant leadership positions. Most frequently these were in workplaces, where security issues, mostly personnel issues could be clarified. These "official" partners were expected not merely to provide information, but also to accept advice from them, and to respect instructions to replace personnel. These contacts could not be considered "unofficial" but they mostly operated in an informal manner. Conversations with "official" Stasi partners could fatefully affect peoples' lives, leading to career difficulties or travel restrictions. The Stasi preferred "official" partners to be members of the nomenklatura.  These were people with close ties to the ruling SED (party), and they were the people who exercised the real power in the East German dictatorship.
Concentration and geographical distributionEdit
The concentration of Informal collaborators varied considerably, ranging from about one IM for every 80 of the population up to about 160. The greatest concentrations were in Cottbus, Schwerin and Magdeburg while the lowest were in Berlin, Halle and Leipzig.
The IM network was almost exclusively a domestic operation. Little information survives on IM activities abroad. It is estimated that the Stasi employed 3,000 (including HVA agents) of these informants in West Germany, and between 300 and 400 in other western countries. During the entire period of the Stasi's existence it is estimated that approximately 12,000 West Germans worked for the Stasi. Many of these were former East Germans whom the Stasi mandated to relocate to the west. The majority of these IMs were nevertheless people born in West Germany who worked for the Stasi because their political sympathies favoured the German Democratic Republic (East Germany).
Genders, party affiliation and age profilesEdit
The 25–40 age group was particularly well represented (between 30 and 40% of IMs fell within this age range as compared with only 24% in the population as a whole), with the under-25s and those of pensionable age correspondingly under represented.
The information collected by the IMs generally involved reports on the behaviour of people from their domestic or work environments. The IMs frequently spied on close friends and family members. After 1989 and the ensuing opening up of the Stasi records, this often led to the terminations of friendships and marriages. Some of the IMs did what they did out of political conviction: others acted in return for favours or because they were put under pressure.
An informal collaborator provided reports, on an average, for between six and ten years, but in some cases might produce surveillance reports for much longer.
Under the generalised term Informal Collaborator (IM) information gathering was also undertaken by people who were not listed as IMs. As an example, that could involve people who simply lived or worked as neighbours of objects deemed relevant to national safety. Additionally, people identified by the Stasi as persistent political adversaries ("Feindlich-negative Personen"), were – each according to his/her importance – subject to surveillance by several IMs recruited for the purpose from among their personal contacts.
From 1957 to 1989 the East German Minister for State Security was a man called Erich Mielke. In Guideline 1/79, which was in effect between 1980 and 1989, Mielke classified the work of the Informal Collaborators as follows:
With special tasks (IMA / Inoffizieller Mitarbeiter mit besonderen Aufgaben)Edit
- IMAs were employed for "offensive" measures in the "Operations region" ("Operationsgebiet"). The "Operations region" meant West Germany. IMA "offensive" measures involved contacts with western journalists in order to plant stories in western media. The work involved both one-time actions and long-running projects. By 1989 the Stasi were working with approximately 16 West German IMAs.
For [homeland] defense with enemy-connections and for the immediate processing of persons suspected of enemy-connected actions (IMB / Inoffizieller Mitarbeiter der Abwehr mit Feindverbindung bzw. zur unmittelbaren Bearbeitung im Verdacht der Feindtätigkeit stehender Personen)Edit
- IMBs were particularly important IMs. They enjoyed the confidence of the Stasi, and they also had direct contacts with people classified by the Stasi as hostile (Feindlich-negative Personen). They had direct involvement with long-running work on developing the relevant Operativer Vorgang (Procedures Manual).
- Some IMBs were permitted to travel outside the Eastern Bloc in order to observe or investigate people or objects. For these objectives they were also provided with secret service materials and foreign currency. The Stasi were particularly interested in opposition groups and church officials, and were keen to recruit, as IMBs, any East German citizens who had relationships with such people in countries outside the Eastern Bloc. The Stasi also favoured, as IMBs, people who had kinship connections to employees of state organisations in West Germany such as the Police service and security services. Where East Germans with such kinship connections became known to the Stasi, attempts were made, sometimes using untoward pressure, to recruit them as IMBs.
- The category of Informal Collaborators classed as IMBs came about from the merger, in 1980, of two other categories, the IMFs and the IMVs Before 1968 they were known, more simply, as "Secret Collaborators" (GMs / "Geheime Mitarbeiter"). On 31 December 1987 the Stasis were working with more than 3,955 IMBs.
On special operations (IME / Inoffizieller Mitarbeiter im besonderen Einsatz)Edit
- IMEs were Informal Collaborators used by the Stasi for specialist missions. They were people with unusual skills, such as handwriting experts or toxicologists, and they were used for surveillance and investigations in key locations. At universities and academies, for example, they could monitor trends in research and development, and highlight administrative shortcomings. Before 1968 they were known as "Secret Collaborators in specialist operations" (GMEs / "Geheime Mitarbeiter im besonderen Einsatz"). In June 1988 the Stasis were listing 7,375 IMEs.
For Protection from Conspiracies and Subversive groupings (IMK / Inoffizieller Mitarbeiter zur Sicherung der Konspiration und des Verbindungswesens)Edit
- IMKs were used by the Stasi for various logistical assignments. There were different types of IMK, depending on the nature of their tasks. Those who set up safe houses, special rooms or objects, were known as IMK/KWs or IMK/KOs. Those providing the Stasi with undercover addresses or undercover telephones were known as IMK/DAs or IMK/DTs IMs providing logistical services on behalf of other East German security organisations are identified in the files with the initials IMK/S. In 1989 the Stasi was working with approximately 30,500 IMKs. In most cases these were people who themselves passed on only small amounts of information to the Stasi but who were valued and trusted because of their importance in the context of conspiracies.
For Political-operative Penetration and for Protection of Responsibility areas (IMS / Inoffizieller Mitarbeiter zur politisch-operativen Durchdringung und Sicherung des Verantwortungsbereiches)Edit
- IMSs were people engaged in security-related areas (such as businesses, social institutions, research and training facilities or governmental institutions) who routinely or regularly reported on other peoples' behaviour. The idea was to identify and prevent suspicious actions as early as possible, and to contribute more generally to domestic security in their areas of responsibility. Before 1968 IMSs were generally known simply by the label "Secret informant" (GI / "Geheimer Informator "). This was the largest of the categories in Informal Collaborator under Mielke's classification system, with 93,600 listed by the Stasi in 1989. Other sources indicate that during the 1980s the proportion of IMs in the IMS category was even higher, at 85%.
(GMS / Gesellschaftliche Mitarbeiter für Sicherheit)Edit
- GMSs were people active in leading positions in the economy and administration, and were often high-profile supporters of the state and of the party. They were used for information retrieval, and might be able, behind the scenes, to ease the workload of other classes of IM. By and large they did not participate directly in operations involving "enemy-negative persons" ("feindlich-negativer Personen"). By the end there were about 33,300 GMSs. Although the GMs partly worked like other classes of IM, the Stasi records did not classify them with the other IMs: GMS operations were conducted according to a separate set of guidelines. Because of this, in disputes over the numbers of IMs, the historian Ilko-Sascha Kowalczuk contends that informants in the GMS category should not be counted as IMs.
Leading IMs (FIM / Führungs-IM)Edit
- Reliable IMs with leadership qualities and "operational experience" could, on behalf of the Stasi - under the leadership and direction of a Stasi operational officer" lead and instruct at most between three and five IMs or GMSs. Their mandate and terms often enabled them to operate with a large measure of independence. Until 1968 they were designated Senior Secret Informers (GHI / Geheime Hauptinformatoren). In June 1988 there were 4,657 of them. In addition the HVA (foreign intelligence) had 26 based in West Germany. There were also around 3,500 professional people in a group described as High-level IM leaders (HFIM / "Hauptamtlichen Führungs-IM ") who appeared to be working in positions of responsibility, but without any formally defined work or military contractual relaitonship, who performed duties on behalf of, and who were paid by, the Stasi. After 1986 these people are listed with the other Stasi employees.
IM candidates and probationary IMs (IM-Kandidat/IM-Vorlauf)Edit
- An individual keen to become an informal collaborator was entered into a preliminary process, and who had started to undertake information gathering conversations, but had not yet been recruited, was listed in the Stasi files as a "probationary IM" ("Vorlauf-IM"/ VL-IM or V-IM ). In this situation a centrally administered IM preliminary programme was followed. Provided the probationary phase was successfully completed, the candidate made a declaration of agreement and became a regular Informal Collaborator (IM). Otherwise the application was cancelled and, under most circumstances, simply archived.
An aspect of the establishment, in October 1990, of the Federal Commission for the Stasi Records (BStU) was the inclusion, intentionally, of numerous former senior Stasi employees. However, at the same time large numbers of unrecognized Informal Collaborators were also recruited. This was possible because the vetting of people recruited to the BStU for evidence of previous Stasi collaboration was extremely lax - far more so than in respect of people recruited to other institutions. For example, the first director of the BStU's Schwerin branch stated publicly: "We had agreed that each one should be self-checking". In 1998 it turned out that a former Stasi IM (identified in Der Spiegel as "IM Delia"), had up to that point been in the director of the BStU's Schwerin branch.
A recurring feature of the analysis of the role of Informal Collaborators in the German Democratic Republic has been a succession of legal actions undertaken against authors in order to try and prevent the naming of former IMs. The courts have sometimes responded with mutually contradictory judgements. A new development came in 2010 with the attempt, initially successful, but which was rejected on appeal, of a former Stasi spy in Erfurt to prevent his name appearing on a website.
The great range of circumstances that led to collaboration with the Stasi makes any overall moral evaluation of the spying activities extremely difficult. There were those that volunteered willingly and without moral scruples to pass detailed reports to the Stasi out of selfish motives, from self-regard, or from the urge to exercise power over others. Others collaborated with the Stasis out of a sincerely held sense of duty that the GDR was the better Germany and that it must be defended from the assaults of its enemies. Others were to a lesser or greater extent themselves victims of state persecution and had been broken or blackmailed into collaboration. Many informants believed that they could protect friends or relations by passing on only positive information about them, while others thought that provided they reported nothing suspicious or otherwise punishable, then no harm would be done by providing the Stasi with reports. These failed to accept that the Stasi could use apparently innocuous information to support their covert operations and interrogations.
A further problem in any moral evaluation is presented by the extent to which information from informal collaborators was also used for combating non-political criminality. Moral judgements on collaboration involving criminal police who belonged to the Stasi need to be considered on a case by case basis, according to individual circumstances.
A belief has gained traction that any informal collaborator (IM) who refused the Stasi further collaboration and extracted himself (in the now outdated Stasi jargon of the time "sich dekonspirierte") from a role as an IM need have no fear of serious consequences for his life, and could in this way safely cut himself off from communication with the Stasi. This is untrue. Furthermore, even people who declared unequivocally that they were not available for spying activities could nevertheless, over the years, find themselves exposed to high-pressure "recruitment" tactics. It was not uncommon for an IM trying to break out of a collaborative relationship with the Stasi to find his employment opportunities destroyed. The Stasi would often identify refusal to collaborate, using another jargon term, as "enemy-negative conduct" ("feindlich-negativen Haltung"), which frequently resulted in what they termed "Zersetzungsmaßnahmen", a term for which no very direct English translation is available, but for one form of which a definition has been provided that begins:
- "a systematic degradation of reputation, image, and prestige in a database on one part true, verifiable and degrading, and on the other part false, plausible, irrefutable, and always degrading; a systematic organization of social and professional failures for demolishing the self-confidence of the individual...".
- Ilko-Sascha Kowalczuk: Stasi konkret. Überwachung und Repression in der DDR. Beck, München 2013, ISBN 978-3-406-63838-1
- Helmut Müller-Enbergs: Die inoffiziellen Mitarbeiter. In: BStU: Anatomie der Staatssicherheit – Geschichte, Struktur, Methoden. Berlin 2008, S. 35–38, 
- Helmut Müller-Enbergs (Hrsg.): Inoffizielle Mitarbeiter des Ministeriums für Staatssicherheit. Teil 1: Richtlinien und Durchführungsbestimmungen. Ch. Links Verlag, Berlin 1996, ISBN 3-86153-101-1.
- Helmut Müller-Enbergs (Hrsg.): Inoffizielle Mitarbeiter des Ministeriums für Staatssicherheit. Teil 2: Anleitung für die Arbeit mit Agenten, Kundschaftern und Spionen in der Bundesrepublik Deutschland. Ch. Links Verlag, Berlin 1998, ISBN 3-86153-145-3.
- Helmut Müller-Enbergs (Hrsg.): Inoffizielle Mitarbeiter des Ministeriums für Staatssicherheit. Teil 3: Statistiken. (Mitarbeit Susanne Muhle) Ch. Links Verlag, Berlin 2008, ISBN 978-3-86153-441-9. auf Google Books
- Jörn Mothes, Gundula Fienbork u.a. (Hrsg.): Beschädigte Seelen. DDR-Jugend und Staatssicherheit. Edition Temmen, Rostock 1996, ISBN 3-86108-881-9.
- Francesca Weil: Zielgruppe Ärzteschaft. Ärzte als inoffizielle Mitarbeiter des Ministeriums für Staatssicherheit der DDR. V & R Unipress, Göttingen 2008, ISBN 3-89971-423-7. (=Hannah-Arendt-Institut für Totalitarismusforschung: Berichte und Studien, Nr. 54)
- Sources differ, however.
- Ilko-Sascha Kowalczuk: Stasi konkret. Überwachung und Repression in der DDR. Beck, München 2013, ISBN 978-3-406-63838-1
- Roger Engelmann, Bernd Florath, Helge Heidemeyer, Daniela Münkel, Arno Polzin, Walter Süß: Das MfS-Lexikon Begriffe, Personen und Strukturen der Staatssicherheit der DDR Ch. Links Verlag, Berlin 2011, ISBN 9783861536277, S. 97
- Bundestags-Drucksache 16/7919 (PDF; 113 kB), Antwort der Bundesregierung auf die Kleine Anfrage der FDP-Fraktion, 29. Januar 2008.
- Figures taken from Helmut Müller-Enbergs: Die inoffiziellen Mitarbeiter. (Table 9, page 36) In: BStU: Anatomie der Staatssicherheit – Geschichte, Struktur, Methoden, Berlin 2008, .
- Helmut Müller-Enbergs (January 2008). "Die inoffiziellen Mitarbeiter (MfS-Handbuch): Anatomie der Staatssicherheit - Geschichte, Struktur und Methoden" (PDF). BStU, Berlin. Retrieved 31 October 2014.
- The 173,081 figures is the headcount at 31 December 1988. It excludes HVA informers. Some sources may aggregate statistics for the two organisations.
- Helmut Müller-Enbergs: IM-Statistik 1985–1989. In: BF informiert 3/93, BStU, Berlin 1993, page 55
- nb/dpa (10 March 2008). "Mehr Stasi-Spitzel als angenommen ...In der DDR wurde offenbar noch mehr geschnüffelt und verraten als bisher angenommen: Die Zahl der Inoffiziellen Mitarbeiter bei der Stasi muss einer Studie zufolge nach oben korrigiert werden". Focus (online). Retrieved 1 November 2014.
- Stefan Berg (21 February 2013). "Neue Studie zu DDR-Spitzeln: Die schlanke Stasi: War der Überwachungsapparat der DDR kleiner als angenommen? Eine neue Studie stellt die hohe Zahl von Spitzeln in Frage - diese habe auf teils abenteuerlichen Rechnungen basiert. Auch das Bild des Stasi-Offiziers wird relativiert: Die Überwacher wurden selbst genauestens beobachtet". Der Spiegel (online). Retrieved 1 November 2014.
- Christian Booß (13 March 2013). "Streit um Stasi-Forschung Der IM, der keiner war: Wer ist als Inoffizieller Mitarbeiter der Stasi zu bewerten - und wer nicht? Das jüngst erschienene Buch des Historikers Ilko-Sascha Kowalczuk "Stasi konkret" hat eine heftige Kontroverse ausgelöst . Unser Autor, wie Kowalczuk bei der Stasiunterlagenbehörde beschäftigt, setzt sich kritisch mit dessen Thesen auseinander". Tagesspiegel (online). Retrieved 1 November 2014.
- Marianne Birthler (BStU 2000-2011) (22 July 2003). "Stasiopfer Diskussionsforum (radio 'phone-in transcript)". ARD (Arbeitsgemeinschaft der öffentlich-rechtlichen Rundfunkanstalten der Bundesrepublik Deutschland ). Retrieved 1 November 2014.
- Weill, Francesca. Zielgruppe Ärzteschaft. Ärzte als inoffizielle Mitarbeiter des Ministeriums für Staatssicherheit (Targeting the medical profession. Doctors as informal collaborators with the Ministry for State Security) (Berichte und Studien 54), Göttingen 2007; Müller-Enbergs, Helmut. Über Ja-Sager und Nein-Sager. In: Hecht, Marco; Praschl, Gerald: Ich habe Nein gesagt. Zivilcourage in der DDR. Berlin 2002, S. 147-166. Ders. Warum wird einer IM? Zur Motivation bei der inoffiziellen Zusammenarbeit mit dem Staatssicherheitsdienst.
In: Behnke, Klaus; Fuchs, Jürgen (Hg.): Zersetzung der Seele. Psychologie und Psychiatrie im Dienste der Stasi. Hamburg 1995, Pages 102-129.
- Sven Felix Kellerhoff (26 September 2014). "Die Stasi hatte viel mehr Informanten als bekannt: Seit den 1990er-Jahren heißt es, jeder 85. DDR-Bürger habe der Staatssicherheit Erkenntnisse geliefert. Eine neue Studie kommt zu einer gänzlich anderen Zahl. Jeder 16. galt als "Auskunftsperson"". Die Welt (online). Retrieved 1 November 2014.
- Matthias Schlegel (1 October 2014). "Erich Mielke und sein geheimes Dossier Die brisanten Akten über die Spitzengenossen: Stasi-Chef Erich Mielke hat einst ein umfangreiches geheimes Dossier über die Spitzengenossen von SED und Regierung anlegen lassen. Ein neues Buch enthüllt erstmals Details zur Ablage "Rote Nelke"". Tagesspiegel (online). Retrieved 1 November 2014.
- Christian Booß, Helmut Müller-Enbergs: Die indiskrete Gesellschaft. Studien zum Denunziationskomplex und zu inoffiziellen Mitarbeitern. Frankfurt (Main): Verlag Polizeiwissenschaft 2014, 268 pages, ISBN 978-3-86676-384-5,
- Jens Gieseke: Die Stasi 1945–1990, München 2011, page 116.
- Figures taken from Helmut Müller-Enbergs: Die inoffiziellen Mitarbeiter. (Table 10, page 38) In: BStU: Anatomie der Staatssicherheit – Geschichte, Struktur, Methoden, Berlin 2008, .
- Figures taken from Helmut Müller-Enbergs: Die inoffiziellen Mitarbeiter. (Pages 35-38) In: BStU: Anatomie der Staatssicherheit – Geschichte, Struktur, Methoden, Berlin 2008, .
- Heinrich August Winkler: Der lange Weg nach Westen. Vol 2: Deutsche Geschichte vom Dritten Reich bis zur Wiedervereinigung. München 2000, page 324.
- Regina Karell: Inoffizielle Mitarbeiterinnen der DDR-Staatssicherheit im Bezirk Gera 1989. Erfurt 2008, ISBN 978-3-932303-61-6, page 100.
- Figures taken from Helmut Müller-Enbergs: Die inoffiziellen Mitarbeiter. (Page 39) .
- Helmut Müller-Enbergs: Inoffizieller Mitarbeiter (IM). in: Roger Engelmann, Bernd Florath, Walter Süß and others. (edited): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 159.
- GMS = "Gesellschaftlicher Mitarbeiter Sicherheit" ("Social Security Employee"), thereby a citizen whose loyalty to the state is publicly known
- IMB = "Inoffizieller Mitarbeiter Beobachtung" ("Informal Collaborator: Observation") for foreign intelligence
- IMS = Inoffizieller Mitarbeiter Sicherheit ("Informal Collaborator: Safety")
- Jens Gieseke. "Mielke, Erich *28.12.1907, † 21.5.2000 Minister für Staatssicherheit; Mitglied des Politbüros des ZK der SED". Bundesstiftung zur Aufarbeitung der SED-Diktatur: Biographische Datenbanken. Retrieved 3 November 2014.
- Helmut Müller-Enbergs: Inoffizieller Mitarbeiter mit besonderen Aufgaben (IMA). In: Roger Engelmann, Bernd Florath, Walter Süß and others (edited): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 161.
- IMF = "Inoffizieller Mitarbeiter der inneren Abwehr mit Feindverbindungen zum Operationsgebiet" ("Informal Collaborator of homeland defense with enemy connections to the Operations region [i.e. to West Germany]")
- IMV = "Inoffizieller Mitarbeiter, der unmittelbar an der Bearbeitung und Entlarvung im Verdacht der Feindtätigkeit stehender Personen mitarbeitet" ("Informal Collaborator with direct involvement in the processing and exposure of suspected enemy activists")
- Helmut Müller-Enbergs: Inoffizieller Mitarbeiter der Abwehr mit Feindverbindung bzw. zur unmittelbaren Bearbeitung im Verdacht der Feindtätigkeit stehender Personen (IMB). In: Roger Engelmann, Bernd Florath, Walter Süß among others (edited): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 160f.
- Ilko-Sascha Kowalczuk: Stasi konkret – Überwachung und Repression in der DDR, München 2013, page 223.
- Helmut Müller-Enbergs: Inoffizieller Mitarbeiter der Abwehr mit Feindverbindung bzw. zur unmittelbaren Bearbeitung im Verdacht der Feindtätigkeit stehender Personen (IMB). In: Roger Engelmann, Bernd Florath, Walter Süß among others (edited): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 161.
- "KW/O" stood here for "Konspiration Wohnung/Objekt" ("Conspiracy Apartment/Object")
- "DA" stood here for "Deckaddressen": "DT" stood for "Decktelefone"("Cover address": "Cover telephone")
- Helmut Müller-Enbergs: Inoffizieller Mitarbeiter zur Sicherung der Konspiration und des Verbindungswesens (IMK). In: Roger Engelmann, Bernd Florath, Walter Süß u. a. (Hrsg.): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 162.
- Vgl. Helmut Müller-Enbergs: Gesellschaftlicher Mitarbeiter für Sicherheit (GMS). In: Roger Engelmann, Bernd Florath, Walter Süß and others (edited): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 101.
- "Erfahrung in der operativen Arbeit"
- "im Auftrag des MfS … unter Anleitung und Kontrolle eines operativen Mitarbeiters ... "
- Abkürzungsverzeichnis der Behörde der/des Bundesbeauftragten für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik
- Vgl. Helmut Müller-Enbergs: Gesellschaftlicher Mitarbeiter für Sicherheit (GMS). In: Roger Engelmann, Bernd Florath, Walter Süß and others (edited): Das MfS-Lexikon – Begriffe, Personen und Strukturen der Staatssicherheit der DDR, Ch. Links Verlag, Berlin 2011, page 156f.
- "Wir waren übereingekommen, dass jeder sich selbst überprüft."
- "STASI IM: Delia im Schweriner Archiv?". Der Spiegel (online). 31 August 1998. Retrieved 9 November 2014.
- Uwe Müller (18 March 2009). "Haben Ex-Stasi-Spitzel ein Recht auf Vergessen? Einst war er der wohl teuerste Stasi-Spitzel in Erfurt. Als IM "Schubert" lieferte Herbert Gräser etwa Informationen gegen die Verteiler von Flugblättern. Heute mag er nicht mehr öffentlich an seine Taten erinnert werden. Deshalb verklagt er einen Ex-Bürgerrechtler, der im Internet auf Gräsers Vergangenheit hinweist". Die Welt (online). Retrieved 9 November 2014.
- H_J_Foeller (17 June 2011). "Klage des Erfurter IM "Schubert" endgültig gescheitert". Retrieved 9 November 2014.
- Roger Engelmann, Frank Joestel: Grundsatzdokumente des MfS. In: Klaus-Dietmar Henke, Siegfried Suckut, Thomas Großbölting (Hrsg.): Anatomie der Staatssicherheit: Geschichte, Struktur und Methoden. MfS-Handbuch. Teil V/5, Berlin 2004, page 287.
- Freya Klier: „In den schmutzigsten Tümpeln der DDR-Geschichte“. Die Welt (online) 6 January 2007
- Der Fall des IM Schubert: „Dürfen wir wissen, wer IM Schubert war?“ taz.de 8 April 2008
- Stasi-Spitzel darf mit Klarnamen genannt werden Die Welt (online) 22 April 2008
- Dossier des Spiegel zu Inoffiziellen Mitarbeitern der Staatssicherheit / Der Spiegel dossiers on individual IMs