proposition: Lemma incident_vset (G : pre_graph) (isG : is_graph G) x e : e \in eset G -> incident G x e -> x \in vset G.
proof: Proof. move => He /existsP[b]/eqP<-. exact: endptP. Qed.
imports: HB(structures) Coq(Relation_Definitions Morphisms RelationClasses) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom rewriting) GraphTheory(finmap_plus)