Let capmx_witnessP m n (A : 'M_(m, n)) : equivmx A (qidmx A) (capmx_witness A).
Let capmx_normP m n (A : 'M_(m, n)) : equivmx_spec A (qidmx A) (capmx_norm A).
Let capmx_nopP m n (A : 'M_(m, n)) : equivmx_spec A (qidmx A) (capmx_nop A).
Let sub_qidmx m1 m2 n (A : 'M_(m1, n)) (B : 'M_(m2, n)) :
qidmx B -> (A <= B)%MS.
Let qidmx_cap m1 m2 n (A : 'M_(m1, n)) (B : 'M_(m2, n)) :
qidmx (A :&: B)%MS = qidmx A && qidmx B.
Let capmx_eq_norm m1 m2 n (A : 'M_(m1, n)) (B : 'M_(m2, n)) :
qidmx A = qidmx B -> (A :&: B)%MS = capmx_norm (A :&: B)%MS.

Lemma capmxSl m1 m2 n (A : 'M_(m1, n)) (B : 'M_(m2, n)) : (A :&: B <= A)%MS.