proposition: Lemma href_sound C : prv ([af C] ---> Bot) -> ~ (exists M : cmodel, sat M C).
proof: Proof. move => H [M] [w] /satA X. exact: soundness H M w X. Qed.
imports: Relations mathcomp.ssreflect.ssreflect mathcomp(all_ssreflect) CompDecModal.libs(edone bcase fset base modular_hilbert sltype)