Section Suma_1.
Context `{TnEQD:Tarski_neutral_dimensionless_with_decidable_point_equality}.
(** Unicity of the sum. *)
(** Commutativity of the sum. *)
(** CongA preserves SumA. *)
(** Out preserves SumA. *)
(** ABC + 0 =  ABC (two lemmas) *)
(** 0 + DEF = DEF (two lemmas) *)
(** Some permutation properties:*)

Lemma suma_left_comm : forall A B C D E F G H I,
SumA A B C D E F G H I -> SumA C B A D E F G H I.