1. (1) American National Standard Instute: American National Standard Z 309. 1964 R 1969, Designation: E112-63
2. (2) N. Grimm: Ceramic Bulletin, 50-12 1971 962 3 J. G. J. Peelen: Philips Tech. Rev. 36 1976 48
3. (3) W. Elenbaas: The high pressure mercury discharge., North Holland Pub Co., 1951 Amsterdom
4. (4) P. L. Denbigh, et. al.: Light. Res- Technol., 18-3 1976 141
5. Light scattering by pores in polycrystalline materials: Transmission properties of alumina