Global Instance IncidLP_morphisml : Proper(EqL ==> eq ==> iff) IncidLP.Global Instance IncidLP_morphismr : Proper(eq ==> EqP ==> iff) IncidLP.

Lemma congH_perml : forall A B C D, A <> B -> C <> D -> CongH A B C D -> CongH B A C D.