∀ {R : Type u_1} {M : Type u_2} {N : Type u_3} [inst : CommSemiring R] [inst_1 : AddCommMonoid M]
  [inst_2 : AddCommMonoid N] [inst_3 : Module R M] [inst_4 : Module R N] (x : TensorProduct R M N),
  ∃ k m n, x = ∑ j, m j ⊗ₜ[R] n j