1. Random fluctuations, persistence, and quasi-persistence in geophysical and cosmical periodicities;Bartels;J. Geophys. Res.,1935
2. Beyer, W. H., , Handbook of Tables for Probability and Statistics, The Chemical Rubber Co., Ohio, 1966,
3. Chapman, S., , J., Bartels, , Geomagnetism, , I, Oxford University Press, New York, 1940,
4. Some phenomena of sunspots and of terrestrial magnetism at Kew Observatory;Chree;Philos. Trans. R. Soc. London,1912
5. Some phenomena of sunspots and of terrestrial magnetism, II;Chree;Philos. Trans. R. Soc. London,1913