Section IsoFitting.
Variables (gT rT : finGroupType) (G D : {group gT}) (f : {morphism D >-> rT}).

Lemma p_abelem_split1 rT p (A : {group rT}) x :
p.-abelem A -> x \in A ->
exists B : {group rT}, [/\ B \subset A, #|B| = #|A| %/ #[x] & <[x]> \x B = A].