A simple method for calculating counterterms

A method for simplifying the evaluation of the infinite parts of Feynman diagrams is presented. It is based on the observation that counterterms are local functions. All integrals are reduced to logarithmically divergent ones with no masses or external momenta. The method is particularly useful for many-point Green's functions at more than one loop. Here a pedagogical approach is taken, using the example of a massive phi3 theory in six dimensions