proposition: Lemma morphim_dprodml A : A \subset H -> dprodm @* A = fH @* A.
proof: Proof. exact: morphim_cprodml. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(choice fintype bigop finset fingroup morphism) mathcomp(quotient action)