proposition: Lemma sf_closed'_mon (X Y : clause) s : sf_closed' X s -> X `<=` Y -> sf_closed' Y s.
proof: Proof. case: s. elim => [|x|s IHs t IHt|s IHs|s IHs t IHt|s IHs t IHt] b H /subP sub //=; rewrite ?sub //=; by [case/andP: H | case/and3P: H]. Qed.
imports: mathcomp.ssreflect.ssreflect mathcomp(all_ssreflect) CompDecModal.libs(edone bcase fset base modular_hilbert sltype)