The strategy of regions for asymptotic expansion of two-loop vertex   Feynman diagrams
  General prescriptions for evaluation of coefficients at arbitrary powers and logarithms in the asymptotic expansion of Feynman diagrams in the Sudakov limit are discussed and illustrated by two-loop examples. Peculiarities connected with evaluation of individual terms of the expansion, in particular, the introduction of auxiliary analytic regularization, are characterized. 
V.A. Smirnov and E.R. Rakhmetov