Section IsogAbelian.
Variables aT rT : finGroupType.
Implicit Type (gT : finGroupType) (D G : {group aT}) (H : {group rT}).
Variables (D : {group aT}) (f : {morphism D >-> rT}).

Lemma morphim_rank_abelian G : abelian G -> 'r(f @* G) <= 'r(G).