End Special.
Section Extraspecial.
Variables (p : nat) (gT rT : finGroupType).
Implicit Types D E F G H K M R S T U : {group gT}.
Section Basic.
Variable S : {group gT}.
Hypotheses (pS : p.-group S) (esS : extraspecial S).
Let pZ : p.-group 'Z(S) := pgroupS (center_sub S) pS.

Lemma exponent_2extraspecial G : 2.-group G -> extraspecial G -> exponent G = 4.