1. Chapman, S. and Cowling, T. G., 1970, “The Mathematical Theory of Non-Uniform Gases,” University Press, Cambridge.
2. Drop, P. C., Fischer, E., Oostvogels, F. and Wesselink, G. A., 1975, Philip. Tech. Rev.,35:347.
3. Elenbaas, W., 1951, “The High Pressure Mercury Vapour Discharge,” North Holland, Amsterdam.
4. Fischer, E., 1974, J. Appl. Phys., 45:3365.
5. Fowler, R. H., 1955, “Statistical Mechanics,” 2nd ed., University Press, Cambridge.