1. Milne, J., ?Experiments in observational seismology?, Trans. Seismol. Soc. Japan. 3 (1881) 12?64.
2. Perry, J., ?Note on the rocking of a column?, Trans. Seismol. Soc. Japan. 3 (1881) 103?106.
3. Milne, J., ?Seismic experiments?, Trans. Seismol. Soc. Japan., 8 (1885) 1?82.
4. Housner, W. G., ?The behavior of inverted pendulum structures during earthquakes?, Bull. Seismol. Soc. Amer., 53 (1963) 403?417.
5. Moreau, J. J., ?Les liaisons unilatérales et let principe de Gauss?, C. R. Acad. Sci. Paris, 256 (1963) 871?874.