proposition: Lemma par2oneone: 1 ∥ 1 ≃2 1.
proof: Proof. etransitivity. apply par2dot=>//. apply dot2one. Qed.
imports: HB(structures) Coq(Setoid Morphisms) mathcomp(all_ssreflect) GraphTheory(edone finite_quotient preliminaries bij equiv) GraphTheory(setoid_bigop structures pttdom mgraph ptt)