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'.