On the product of affine manifolds and the generalized de Rham splitting theorem
A de Rham decomposition theorem for arbitrary affine connections, satisfying a certain curvature condition, is proved. This generalizes the theorems of de Rham or \textit{S. Kobayashi} and \textit{K. Nomizu} [Foundations of differential geometry, Vols. I and II, Interscience (New York 1963; Zbl 0119.375 and 1969; Zbl 0175.485)]. The very elaborate proof follows closely that from the book cited above.
scientific article; zbMATH DE number 508822