(* the following properties are useful for studying p-groups of class 2 *)
Variables (i : nat) (x y : gT).
Hypothesis cxz : commute x [~ x, y].

(* Specifications: *)
Lemma commVg : [~ x^-1, y] = [~ x, y]^-1.
Lemma commXg : [~ x ^+ i, y] = [~ x, y] ^+ i.
End LeftComm.