“…Following this, by using deep group theory, all symmetric graphs of order 2p, 3p or qp were classified in [5,34,29,30], where p, q are distinct primes. Recently, Li [22] classified vertex-primitive and vertex-biprimitive s-transitive graphs for s ≥ 4, and Fang et al [8] classified vertex-primitive 2-regular graphs. For more results on symmetric graphs with general valencies, see, for example, [10,20,21,22].…”