End Cprodm.
Section Dprodm.
Variables G H K : {group gT}.
Variables (fH : {morphism H >-> rT}) (fK : {morphism K >-> rT}).
Hypothesis eqHK_G : H \x K = G.
Hypothesis cfHK : fK @* K \subset 'C(fH @* H).

(* Specifications: *)
Lemma dprodm_cprod : H \* K = G.
Lemma dprodm_eqf : {in H :&: K, fH =1 fK}.
End Dprodm.
Lemma isog_dprod A B G C D L :
A \x B = G -> C \x D = L -> isog A C -> isog B D -> isog G L.