Definition ulsubmx := lsubmx (usubmx A).Definition ursubmx := rsubmx (usubmx A).Definition dlsubmx := lsubmx (dsubmx A).Definition drsubmx := rsubmx (dsubmx A).

Lemma block_mxEdr i j : A (rshift m1 i) (rshift n1 j) = Adr i j.