proposition: Lemma path_sum_assoc X Y Z : X + (Y + Z) = X + Y + Z.
proof: Proof. symmetry. apply path_universe_uncurried. apply equiv_sum_assoc. Qed.
imports: HoTT(TruncType ExcludedMiddle abstract_algebra) HoTT(PropResizing.PropResizing) HoTT(Spaces.Nat.Core Spaces.Card) HoTT(Equiv.BiInv) HoTT(HIT.unique_choice) HoTT.Sets(Ordinals Hartogs Powers GCH AC)