[en] In an arbitrary theory a generating functional of Green functions of anti psi(x)Opsi(x) (o-matrix) combinations may be written down as a generating functional in some scalar theory. The aim of the paper is to clarify in what theory exactly it may be done. The transformation of the functional integral from Fermi fields to scalar ones has been done. The validity of this method is illustrated in some certain examples. The existence of the massive fermionic mode in some nonabelian massless model with a current-current interaction has been proved