“…Various generalizations of the Petersen graph have been considered [21,22,34,35,37,67,95,106,122,123,162,163,1701, including methods of constructing class-two graphs. Other similar constructions not related to the Petersen graph are to be found in [14,52,57,60,102,1411. Most works of a general nature, such as [8,9,11,15,82,165,168, 1711 include a treatment of bipartite graphs and of complete graphs.…”