Qed.
(** Proof that A is valid iff NNF A is valid*)

Lemma NNF_equiv_valid : forall v A, TrueQ v (NNFtoPropF (MakeNNF  A))=TrueQ v  A /\
TrueQ v (NNFtoPropF (MakeNNFN A))=TrueQ v ¬A.