1. “On Nonlinear Differential Equations, The Maximum Operation, and Monotone Convergence,”;Kalaba;J. Math. Mech.,1959
2. Quasilinearization and Nonlinear Boundary-value Problems;Bellman,1965
3. “A Novel Approach to Elementary Scattering Theory”;Calogero;Nuovo Cimento,1963
4. “A Variational Principle for Scattering Phase Shifts,”;Calogero;Nuovo Cimento,1963
5. “A Note on the Riccati Equation,”;Calogero;J. Math. Phys.,1963