simpl in |- *; auto.
Qed.

Theorem canonical_spminusf :
forall (a b : Term A n) (nZb : ~ zeroP (A:=A) A0 eqA (n:=n) b)
(p q : list (Term A n)),
canonical A0 eqA ltM p ->
canonical A0 eqA ltM q ->
divP A A0 eqA multA divA n a b ->
canonical A0 eqA ltM (spminusf a b nZb p q).