The {β}-expansion formalism in perturbative QCD and its extension

We discuss the {beta}-expansion for renormalization group invariant quantities tracing tins expansion to the different contractions of the corresponding incomplete BPHZ R-operation. All of the coupling renormalizations, which follow from these contractions, should be taken into account for the {beta}-expansion. We illustrate this feature considering the nonsinglet Adler function D-NS in the third order of perturbation. We propose a generalization of the {beta}-expansion for the renormalization group covariant quantities - the {beta, gamma}-expansion.