1. Arking, A., Space Research 4: 133 (1963).
2. Bent R. B. paper given at Fourth International Conference on Universal Aspects of Atmospheric Electricity Tokyo (1968).
3. GEOPHYSICAL MEMOIRS 1925 24 The distribution of thunderstorms over the globe
4. Coroniti S. C. paper given at the International Astronautical Congress Madrid (1966).
5. Humphreys, W. J., Physics of the Air: CH17 (1929).