Section InternalGroupAction.
Variable gT : finGroupType.
Implicit Types A B : {set gT}.
Implicit Types G H : {group gT}.
Implicit Type x : gT.
(*  Various identities for actions on groups. *)

Lemma astabsQ G H : H <| G -> 'N(G / H | 'Q) = 'N(H) :&: 'N(G).