1. Becquerel, H.Annales de Phys. et Chem., 1877,12, 32.
2. Darwin and WatsonProc. Roy. Soc., Lond., 1927,114 A, 474.
3. Landau, S.Phys. Z. S., 1908;9, 417.
4. Mayer, V.Ann. d. Phys., 1909, (4)30, 625.
5. Ramaseshan, S.Proc. Ind. Acad. Sci., 1946,24 A, 104.