ABSTRACT
For scalar fields, which describe bosons, we used real or complex numbers, the eigenvalues of the operators, in order to perform the path integral. For fermionic fields it is essential to build the anticommuting properties into the path integral. By declaring the derivative to be a linear function on the Grassmann algebra, it can be uniquely extended to this algebra from the set of rules. These rules imply that the Grassmann integral over a total Grass-mann derivative vanishes. This chapter summarises the Feynman rules that correspond to the fermionic pieces in computing the reduced matrix elements. For conventions where momenta always flow in the direction of the fermion arrow, the four momenta for wave-function factors associated to in- and outgoing antiparticles should be reversed.
