Definition spolyf :
  forall (p q : list (Term A n)) (Cp : canonical A0 eqA ltM p)
    (Cq : canonical A0 eqA ltM q), list (Term A n).

Theorem spoly_is_minus : forall (a b : Term A n) (nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a) (nZb : ~ zeroP (A:=A) A0 eqA (n:=n) b) (p q : list (Term A n)) (Cpxa : canonical A0 eqA ltM (pX a p)) (Cpxb : canonical A0 eqA ltM (pX b q)), eqP A eqA n (spolyf (pX a p) (pX b q) Cpxa Cpxb) (minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec (mults (A:=A) multA (n:=n) (divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) (ppc (A:=A) A1 (n:=n) a b) (b:=a) nZa) (pX a p)) (mults (A:=A) multA (n:=n) (divTerm (A:=A) (A0:=A0) (eqA:=eqA) divA (n:=n) (ppc (A:=A) A1 (n:=n) a b) (b:=b) nZb) (pX b q))).