  A careful and complete discussion is given of the renormalization of the
singlet axial anomaly equation in a vector-like nonabelian gauge theory such as
QCD regularized by ordinary dimensional regularization. Pseudotensorial
structures are treated with the 't Hooft-Veltman prescription. A general
framework for calculations is developed, and subsequently verified by explicit
computations through two loops. This is followed by a discussion of the matrix
elements obtained.
