1. I. W. Busbridge, The Mathematics of Radiative Transfer, Cambridge University Press, Cambridge, 1960.
2. S. Chandrasekhar, Radiative Transfer, Dover Publications, New York, 1960.
3. V. Kourganoff, Basic Methods in Transfer Problems, Dover Publications, New York, 1963.
4. V. V. Sobolev, Light Scattering in Planetary Atmospheres, Pergamon Press, New York, 1974.
5. R. Bellman, R. Kalaba and M. Prestrud, Invariant Imbedding and Radiative Transfer in Slabs of Finite Thickness, American Elsevier Publishing Co., New York, 1963.