Definition Rstar_S_Rstar :=
   explicit_comp_rel _ (explicit_star _ R)
     (explicit_comp_rel _ S (explicit_star _ R)).Goal
forall f g h : A,
explicit_star _ R f g -> Rstar_S_Rstar g h -> Rstar_S_Rstar f h.Save comp_l.Goal
forall f g h : A,
Rstar_S_Rstar f g -> explicit_star _ R g h -> Rstar_S_Rstar f h.Save comp_r.Goal
forall f g h : A,
explicit_star _ R f h ->
S f g -> exists k : A, explicit_star _ R g k /\ Rstar_S_Rstar h k.Save commut2.

Theorem Yokouchi : explicit_strong_confluence _ Rstar_S_Rstar.