Definition PtoS :
  list (poly A0 eqA ltM) * list (poly A0 eqA ltM) -> sigS FPset.Definition RL (x y : list (poly A0 eqA ltM) * list (poly A0 eqA ltM)) :
  Prop := Co (PtoS x) (PtoS y).

Theorem wf_RL : well_founded RL.