End Subnormal.
Arguments subnormalP {gT H G}.
Section MorphSubNormal.
Variable gT : finGroupType.
Implicit Type G H K : {group gT}.

(* Specifications: *)
Lemma morphim_subnormal (rT : finGroupType) G (f : {morphism G >-> rT}) H K :
H <|<| K -> f @* H <|<| f @* K.
Lemma quotient_subnormal H G K : G <|<| K -> G / H <|<| K / H.
Lemma maximal_exists H G :
H \subset G ->
H :=: G \/ (exists2 M : {group gT}, maximal M G & H \subset M).
Lemma mulg_normal_maximal G M H :
M <| G -> maximal M G -> H \subset G -> ~~ (H \subset M) -> (M * H = G)%g.