On the Migdal-Makeenko Equation for Simple and Nonsimple Contours

The Migdal-Makeenko equation differs explicitely in the abelian and nonabelian case for simple smooth contours already. This is due to endpoint singularities of gauge noninvariant functionals which appear in the nonabelian equation providing anomalous finite contributions in the course of renormalization. Corresponding results are discussed for nonsimple contours.