End GeneralExponentPextraspecialTheory.

(* A special case of the uniqueness half of Achsbacher (23.14). *)
Lemma card_isog8_extraspecial (gT : finGroupType) (G : {group gT}) :
#|G| = 8 -> extraspecial G -> (G \isog 'D_8) || (G \isog 'Q_8).