State the theorem allowing the product of two series of complex numbers. (We admit in the rest of Part III that the result valid for series of complex numbers still holds for series of matrices in $\mathcal{M}_d(\mathbb{C})$.)
State the theorem allowing the product of two series of complex numbers. (We admit in the rest of Part III that the result valid for series of complex numbers still holds for series of matrices in $\mathcal{M}_d(\mathbb{C})$.)