  One of the most important mathematical tools necessary for Quantum Field
Theory calculations is the field propagator. Applications are always done in
terms of plane waves and although this has furnished many magnificent results,
one may still be allowed to wonder what is the form of the most general
propagator that can be written. In the present paper, by exploiting what is
called polar form, we find the most general propagator in the case of spinors,
whether regular or singular, and we give a general discussion in the case of
vectors.
