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2. R. Bellman and G. M. Wing, An Introduction of Invariant Imbedding, SIAM, Philadelphia, 1962.
3. C. F. Bohren, ed., Selected Papers on Scattering in the Atmosphere, SPIE Optical Engineering Press, Bellingham, Washington, 1989.
4. I. W. Busbridge, The Mathematics of Radiative Transfer, Cambridge University Press, Cambridge, 1960.
5. S. Chandrasekhar, Radiative Transfer, Dover Publications, New York, 1960.