End DsumRepr.
Section ProdRepr.
Variables (n1 n2 : nat) (rG1 : reprG n1) (rG2 : reprG n2).

(* Specifications: *)
Lemma prod_mx_repr : mx_repr G (fun g => tprod (rG1 g) (rG2 g)).
Definition prod_repr := MxRepresentation prod_mx_repr.