proposition: Lemma phi_bij : bijective phi.
proof: Proof. by exists phi_inv; first exact: phiK; exact: phi_invK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq path) mathcomp(ssralg fintype finfun perm matrix bigop zmodp mxalgebra) mathcomp(choice poly polydiv mxpoly binomial)