The proof is given in Romer (1983, theorem 3). The assumption on the asymptotic growth of F is self-explanatory. The assumption on the asymptotic exponent of Dg is sufficient to ensure the boundedness of g. The condition on D_1f will be satisfied in most cases in which F(k) = f(k, Sk) is convex. Examples of functions satisfying these assumptions are given in the next section.