1. Franklin, Benjamin: Experiments and Observations on Electricity (1774), edit. by J. B. Cohen. Harvard Univ. Press 1941.
2. Kähler, K.: Die Elektrizität der Gewitter. Berlin: Gebrüder Borntraeger 1924.
3. Bruce, C. E. R., and R. H. Golde: J. Inst. Electr. Engrs. 88, Pt. II, 487 (1941).
4. Wilson, C. T. R.: Phil. Trans. Roy. Soc. Lond., Ser. A 221, 73 (1920). (With reference [10], the classical paper on the subject of the lightning discharge.)
5. Malan, D. J.: Unpublished work. I am grateful to Dr. Malan for permission to use this information.