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 unage_join1 : forall x x' y' z', join x' y' z' -> age x x' ->
exists y, exists z, join x y z /\ age y y' /\ age z z'.