1. H. Wolter, in Handbuch der Physik, edited by S. Flugge ( Springer, Berlin, 1956 ), p. 461.
2. P. H. Berning in Physics of Thin Films, edited by G. Hass, Vol. 1, p. 69, Academic (1963).
3. S. Heavens, Optical Properties of Thin Films, Dover (1965).
4. A. Vasicek, Optics of Thin Films, North Holland (1960).
5. F. Abeles, in Progress in Optics, Vol. II edited by E. Wolf,p.251 North Holland (1963).