New Methods of Integration in Matrix Models
  We discuss a new method of integration over matrix variables based on a suitable gauge choice in which the angular variables decouple from the eigenvalues at least for a class of two-matrix models. The calculation of correlation functions involving angular variables is simple in this gauge. Where the method is applicable it also gives an extremely simple proof of the classical integration formula used to reduce multi-matrix models to an integral over the eigenvalues. 
A.D'Adda