intros x H'; apply Upper_Bound_definition; auto with sets.
intros y H'0; elim H'0; auto with sets.
Qed.
Hint Resolve Anyone_is_Upper_Bound_of_Empty_set.

Theorem Empty_set_has_lub :
forall C : Cpo U, exists bsup : U, Lub U (PO_of_cpo U C) (Empty_set U) bsup.