1. Bateman, H. (1914).The Mathematical Analysis of Electrical and Optical Waves Motions [Reprint Dover, New York (1955)].
2. Campolattaro, A. A. (1980).International Journal of Theoretical Physics,19, 99.
3. Corson, E. M. (1953).Introduction to Tensors, Spinors and Relativistic Wave Equations, Hafner.
4. Eriksen, J. L. (1960). Principles of classical mechanics and field theory, inHandbuch der Physik, Vol. III, Springer, New York.
5. Good, Jr. R. H. (1957).Physical Review,105, 1914.