fact: Variable similar_congr_Plus : forall a b c d, similar a b -> similar c d -> similar (Plus a c) (Plus b d).
imports: Coq(RelationClasses) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq fintype) mathcomp(bigop path) RegLang(languages) RegexpBrzozowski(glue gfinset regexp finite_der)