1. A very full account of the problem will be found in R. K. Luneberg's mimeographed lectures, The Mathematical Theory of Optics, delivered at Brown University in 1944. Luneberg's account depends on certain integral equations equivalent to Maxwell's equations. Cf. Bateman, Partial Differential Equations of Mathematical Physics, Cambridge, 1932, pp. 192–196.
2. and , Methoden der mathematischen Physik, Volume II, Springer, Berlin, 1937, pp. 469–470. Photo-Lithoprint reproduction, Interscience, New York, 1943.