  We present the Vector Equivalence technique. This technique allows a simple
and systematic calculating of Feynman diagrams involving massive fermions at
the matrix element level. As its name suggests, the technique allows two
Lorentz four-vectors to serve as an equivalent of two external fermions. In
further calculations, traces involving these vectors replace the matrix element
with the external fermions. The technique can be conveniently used for both
symbolic and numeric calculations.
