1. On the principle of invariant imbedding and propagation through inhomogeneous media;Bellman,1956
2. An Introduction to Transport Theory;Wing,1962
3. Stochastic equations in radiative transfer by invariant imbedding;Ueno;J. Math. Anal. Appl.,1961
4. Invariant imbedding and scattering theory;Wang;J. Math. Appl.,1967
5. On the principle of invariant imbedding and propagation through inhomogeneous media;Bellman,1956