CANONICAL QUANTIZATION OF INTERACTING WZW THEORIES

Using canonical quantization we find the Virasoro centre for a class o f conformally invariant interacting Wess-Zumino-Witten theories. The t heories have a group structure similar to that of Toda theories (both abelian and non-abelian) but the usual Toda constraints on the couplin g constants are relaxed and the theories are not necessarily integrabl e. The general formula for the Virasoro centre is compared to that der ived by BRST methods in the Toda case, and helps to explain the struct ure of the latter.