TENSOR REDUCTION OF 2-LOOP VACUUM DIAGRAMS AND PROJECTORS FOR EXPANDING 3-POINT FUNCTIONS

Explicit general formulae for the tensor reduction of two-loop massive vacuum diagrams are presented. The problem of calculating the corresp onding coefficients is shown to be equivalent to the problem of constr ucting differential operators (projectors) extracting the coefficients of the momentum expansion of massive scalar three-point functions (wi th any number of loops), so the solution to the latter problem is also given.