Canonical Structure trowb_linear n1 m2 n2 B := 
  Linear (@trowb_is_linear n1 m2 n2 B).Canonical Structure trow_linear n1 m2 n2 A := 
  Linear (@trow_is_linear n1 m2 n2 A).: {group gT}).
Local Notation reprG := (mx_representation R G).

Record representation :=: {group gT}).
Local Notation reprG := (mx_representation R G).

Record representation :=: {group gT}).
Local Notation reprG := (mx_representation R G).

Record representation :=: {group gT}).
Local Notation reprG := (mx_representation R G).

Record representation :=R]_0).
Proof. by split=> // g h Hg Hx; rewrite mulmx1. Qed.

(* Specifications: *)
Lemma add_mx_repr (rG1 rG2 : representation) :