Variables (n : nat) (rG : mx_representation F G n).

(* Specifications: *)
Lemma gring_mxP a : (gring_mx rG a \in enveloping_algebra_mx rG)%MS.
Lemma rsim_regular_series U (compU : mx_composition_series aG U) :
(last 0 U :=: 1%:M)%MS ->
exists i : 'I_(size U), mx_rsim rG (series_repr i compU).