Instance Canc_knot(Canc_F: forall A, Canc_alg (F A)) : Canc_alg knot.Instance Disj_knot(Disj_F: forall A, Disj_alg (F A)) : Disj_alg knot.

Lemma age_join1 : forall x y z x' : K'.knot, join x y z -> age x x' -> exists y' : K'.knot, exists z' : K'.knot, join x' y' z' /\ age y y' /\ age z z'.