proposition: Fact polyOver_mul1_closed : 1 \in (polyOver S).
proof: Proof. by rewrite polyOverC rpred1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)