1. Bellman, R., ‘On Variation Diminishing Properties of Green’s Functions’, Boll. D’Unione Math. 16 (1961), l64.
2. Bellman, R., ‘Oscillatory and Unimodal Properties of Solutions of Second Order Differential Equations’, Bull. U.M.I. 10 (1964), 306.
3. Bellman, R. and S. Lehman, ‘Functional Equations in the Theory of Dynamic Programming - X: Resolvents Characteristic Functions and Values’, Duke Mathematical Journal 27 (1960), 55.
4. Miller, K.S. and M.M. Schiffer, ‘On the Green’s Functions of Ordinary Differential Equations’, Proceedings of the American Mathematical Society 3 (1952), 433.
5. Bellman, R. and H. Osborn, ‘Dynamic Programming and the Variation of Green’s Functions’, Journal of Mathematics and Mechanics 7 (1958), 81.