“…Applying Theorem 1.2, we can obtain the following corollary. The graph Cos(G, a , b ) was first constructed in [19] as a regular cover of K p,p , where it is said that Cos(G, a , b ) is 2-arc-transitive in [19, Theorem 1.1], but not 3-arctransitive generally for all odd primes p in a remark after [19,Example 4.1]. However, this is not true and Corollary 1.3 implies that Cos(G, a , b ) is always 3-arc-transitive for each odd prime p. In fact, Cos(G, a , b ) is 3-arc-regular, that is, Aut(Cos(G, a , b )) is regular on the set of 3-arcs of Cos(G, a , b ).…”