1. Regener, E. and Regener, V.H., Phys. Zeit, 35, 1934;
2. Regener, E. and Regener, V.H., Nature, 134, 380
3. Regener, E., 1935, Beitr Phys. Frei. Atmos., 22, 249.
4. Friedman, H., 1960, Physics of the Upper Atmosphere, Ed. J.A. Ratcliffe, Academic Press, p. 133.
5. Ghosh, S.N. and Dasgupta, S.R., 1978, Sci.and Culture, 44, 437.