Arguments sumsmx_sup i0 [P m n A B_].

Lemma sub_capmx_gen m1 m2 m3 n (A : 'M_(m1, n)) (B : 'M_(m2, n)) (C : 'M_(m3, n)) :
(A <= capmx_gen B C)%MS = (A <= B)%MS && (A <= C)%MS.