Section PlusWf.
Variable X: Set.
Variable S: relation X.
Variable TX: relation X.
Hypothesis HS: diagram TX S (star TX) (plus S).
Hypothesis Hwf: well_founded (trans S).
Let Hpwf: well_founded (trans (plus S)) := plus_wf Hwf.

(** Lemma 4.1 *)
Lemma diagram_plus_wf: diagram (star TX) (plus S) (star TX) (plus S).