For instance, let be an infinite set, the product ring and A the set of homomorphisms given by evaluation at all the elements of . Then the hypothesis of the Lemma holds, but is the product ring which is not in general free as a k-module.
2003, Erdoğan S. Şuhubi, Functional Analysis, Springer, page 63:
Thus the set becomes a ring with these operations and it is called the product ring. The identity element of the product ring with respect to the addition is obviously where 0 and 0 are identity elements of addition in the rings and respectively.
2007, Catriona Maclean (translator), Daniel Perrin, Algebraic Geometry: An Introduction, [1995, D. Perrin, Géométrie algébrique], Springer, page 101,