1. J.J. Thomson and G. P. Thomson, Conduction of Electricity Through Gases, Vol. 2, Cambridge University Press, London, 1933, p. 258.
2. M. de Broglie, J. Phys., Vol. 5, No. 161, 1916, p. 227; Compt. rend., Vol. 163, No. 87, 1916, p. 352.
3. A.H. Compton and S.K. Allison, X-Ray in Theory and Experiment, D. Van Nostrand Co., Princeton, 1947.
4. G.L. Clark, Applied X-Rays, 4th ed., McGraw-Hill Co, New York, 1955.
5. Handbook of Chemistry and Physics, 41st edition, Chemical Rubber Publishing Co., 1959.