proposition: Theorem Cayley_isog G : G \isog Cayley_repr G @* G.
proof: Proof. exact: isom_isog (Cayley_isom G). Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(fintype bigop finset fingroup morphism perm) mathcomp(automorphism quotient)