proposition: Fact proj1_proof : pres M %| pres dsum *m (col_mx 1%:M 0).
proof: Proof. by rewrite mul_block_col !mulmx0 !addr0 mul0mx mulmx1 dvd_mx_col dvdmx0 andbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype perm choice matrix bigop zmodp mxalgebra poly) ssrcomplements stronglydiscrete coherent edr