(* Autor(s): Andrej Dudenhefner (1) Affiliation(s): (1) Saarland University, Saarbrücken, Germany *)
Local Notation "A ≡ B" := (mset_eq A B) (at level 65).
Arguments mset_eq !A !B.

Lemma eq_appI {A B A' B'} : A ≡ A' -> B ≡ B' -> A ++ B ≡ A' ++ B'.