On the nonorientable genus of some generalized Petersen graphs G(n, k) with d == G.C.D.(n, k) > I*

We deal with the graphs G(n, k), which are a generalization of the Petersen graph. If d = G.C.D(n, k) > 1, we classify the "mixed cycles" of length l < 8 and we consider the compatibility of the mixed cycles related to the 2-cell embedding of G(n, k) in a surface. Moreover, we study the nonorientable genus of particular graphs and of particular classes of graphs.