1. Born, M.: Optik, p. 267. Berlin: Springer 1933.
2. See for example F. Stern: In: Solid State Physics, Vol. 15, edit. by F. Seitz, and D. Turnbull, p. 300. New York: Academic Press 1963.
3. Seltz, F.: Modern Theory of Solids. New York: McGraw Hill Book Co. 1939.
4. Fröhlich, H.: Electronentheoric der Metalle. Berlin: Springer 1936.
5. Fröhlich, H., Wilson, A.H.: Theory of Metals. Cambridge: Cambridge University Press 1936.