In this paper we generalize the result obtained by Gonzales Dominguez, Scar
fiello and Fisher (A. Gonzales Dominguez and R. Scarfiello, Rev. Un. Mat. A
rgentina, Volumen de Homenaje a Beppo Levi (1956) 58-67; B. Fisher, Proc. C
ambridge Philos. Soc. 72 (1972) 201-204). This result can be used in quantu
m field theory for the evaluation of products of propagators of the fields.
With this new result we obtain the product (c(2)+P)(-n) . delta (m-1)(c(2)
+P). As a physical example, we evaluate the self-energy Green function of a
massless scalar field.