Definition wk_split {A} {JA: Join A} :=
      forall a b c d e : A, join a b c -> join d e c -> joins a d -> join_sub d b.

Lemma crosssplit_wkSplit {A} {JA: Join A}{PA: Perm_alg A}{SA: Sep_alg A}{DA: Disj_alg A}{CrA: Cross_alg A}{AG: ageable A}{XA: Age_alg A}: wk_split.