For each <math> u_{ij} </math> equation, the columns of <math> D </math> correspond to thea block of <math> um </\math> components in <math> u </math>:
:<math>
</math>
while the columns of <math> I </math> to the left and right of <math> D </math> each correspond to theother blocks of <math> um </\math> components within <math> u </math>: