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

Lemma tr_block_mx : (block_mx Aul Aur Adl Adr)^T = block_mx Aul^T Adl^T Aur^T Adr^T.