1. I. W. Busbridge:The Mathematics of Radiative Transfer (Cambridge University Press, Cambridge, 1960).
2. S. Chandrasekhar:Radiative Transfer (Dover, New York, N.Y., 1960).
3. See, for instance,A. J. Jerri:Introduction to Integral Equations with Applications (Marcel Dekker, New York, Basel, 1985), Chapt. 3.
4. G. Dattoli, A. Renieri andA. Torre:Lectures on the Free Electron Laser Theory and Related Topics (World Scientific, Singapore, 1993).
5. G. Dattoli, L. Giannessi, L. Mezi, A. Torre andR. Caloi:Nucl. Instrum. Methods A,304, 541 (1991).