Definition Dmult :
  forall (a : Term A n) (nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a),
  list (Term A n) -> list (Term A n) -> list (Term A n).

Theorem sp_Rminus : 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 (pX a p) -> canonical A0 eqA ltM (pX b q) -> eqP A eqA n (Rminus b nZb (minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec (mults (A:=A) multA (n:=n) b p) (mults (A:=A) multA (n:=n) a q)) (pX b q) (mults (A:=A) multA (n:=n) b p)) (mults (A:=A) multA (n:=n) (invTerm (A:=A) invA (n:=n) (T1 A1 n)) (multpf A A0 eqA plusA multA eqA_dec n ltM ltM_dec (pX a p) q)).