On invariant quantization of non-Abelian gauge fields
  A strong coupling expansion around the non-trivial extremum of the Yang-Mills action will be described. It is shown that the developed formalism is the Gribov ambiguity free and each order of the developed perturbation theory is transparently gauge invariant. The result is a consequence of the restriction: calculations are not going beyond the module square of the $S$-matrix elements. 
J. Manjavidze
hep-th