Definition spminusf (a b : Term A n) (nZb : ~ zeroP (A:=A) A0 eqA (n:=n) b)
  (p q : list (Term A n)) :=
  minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec p
    (mults (A:=A) multA (n:=n)
       (divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) a (b:=b) nZb) q).

Theorem sp_rew : forall (a b : Term A n) (nZ1 nZ2 : ~ zeroP (A:=A) A0 eqA (n:=n) b) (p q : list (Term A n)), spminusf a b nZ1 p q = spminusf a b nZ2 p q.