Lemma issymmabgrdiffrel (X : abmonoid) {L : hrel X} (is : isbinophrel L) (isl : issymm L) : issymm (abgrdiffrel X is). Proof. refine (issymmquotrel _ _). apply issymmabgrdiffrelint. - apply is. - apply isl. Defined.
Require Import UniMath.MoreFoundations.Orders. Require Import UniMath.MoreFoundations.Subtypes.