Green functions of 2-dimensional Yang-Mills theories on nonorientable   surfaces
  By using the path integral method , we calculate the Green functions of field strength of Yang-Mills theories on arbitrary nonorientable surfaces in Schwinger-Fock gauge. We show that the non-gauge invariant correlators consist of a free part and an almost $x$-independent part. We also show that the gauge invariant $n$-point functions are those corresponding to the free part , as in the case of orientable surfaces. 
M.Alimohammadi and M.Khorrami(IPM,Tehran,Iran)