1. The Method of Multiple Working Hypotheses
2. Foote, A. E., Proceedings of the American Association for the Advancement of Science 40: 279 (1891).
3. Johnson personal communication.
4. Sekiya, Trans. Seismological Soc. of Japan 13: 139 (1890).
5. Scrope, G. P., Volcanos: 369 (1872).