Lemma Qquadratic_sg_denom_nonzero_nonzero_inf : forall (e f g h : Z) (p1 p2 : Qpositive), Qquadratic_sg_denom_nonzero e f g h p1 p2 -> {e <> 0%Z} + {f <> 0%Z} + {g <> 0%Z} + {h <> 0%Z}.