1. Invariant imbedding and mathematical physics—I: Particle processes;Bellman;J. Math. Phys.,1960
2. Invariant Imbedding and Radiative Transfer in Slabs of Finite Thickness;Bellman,1963
3. Invariant imbedding and neutron transport theory—III: Neutron-neutron collision processes;Bellman;J. Math. Mech.,1959
4. Novel uses of functional equations;Redheffer;J. Rat. Mech. Anal.,1954
5. On the fundamental equations of invariant imbedding—I;Bellman,1961