intros l1 l2 l3 H'; elim H'; auto.
intros a1 a2 l4 l5 l6 H'0 H'1 H'2 H'3 H'4; try assumption.
apply order_plusP with (l1 := l4) (l2 := pX a2 l5); auto.
apply canonical_cons; auto.
apply (canonical_nzeroP _ A0 eqA _ ltM) with (p := l4); auto.
apply H'2; auto.
apply (canonical_imp_canonical _ A0 eqA _ ltM) with (a := a1); auto.
intros a1 a2 l4 l5 l6 H'0 H'1 H'2 H'3 H'4 H'5.
apply H'1; auto.
apply (canonical_imp_canonical _ A0 eqA _ ltM) with (a := a1); auto.
apply (canonical_imp_canonical _ A0 eqA _ ltM) with (a := a2); auto.
intros a1 a2 l4 l5 l6 H'0 H'1 H'2 H'3 H'4 H'5.
apply order_plusP with (l1 := l4) (l2 := l5); auto.
apply canonical_pX_eqT with (a := a1); auto.
apply (eqT_sym A n (plusTerm (A:=A) plusA (n:=n) a1 a2)).
apply plusTerm_eqT1; auto.
apply canonical_pX_eqT with (a := a2); auto; auto.
apply (eqT_sym A n (plusTerm (A:=A) plusA (n:=n) a1 a2)).
apply plusTerm_eqT2; auto.
apply H'1.
apply (canonical_imp_canonical _ A0 eqA _ ltM) with (a := a1); auto.
apply (canonical_imp_canonical _ A0 eqA _ ltM) with (a := a2); auto.
intros a1 a2 l4 l5 l6 H'0 H'1 H'2 H'3 H'4.
apply order_plusP with (l1 := pX a1 l4) (l2 := l5); auto.
apply canonical_cons; auto.
apply (canonical_nzeroP _ A0 eqA _ ltM) with (p := l5); auto.
apply H'2; auto.
apply canonical_imp_canonical with (a := a2); auto.
Qed.

Theorem canonical_pluspf :
forall l1 l2,
canonical A0 eqA ltM l1 ->
canonical A0 eqA ltM l2 -> canonical A0 eqA ltM (pluspf l1 l2).