1. B. Dubuc et al.: Proc. R. Soc. London A425, 113 (1989)
2. K.C. Clarke, D.M. Schweizer: Cart. Geog. Inf. Syst.18, 37 (1991)
3. C.Y. Poon, R.S. Sayles, T.A. Jones: J. Phys. D25, 1269 (1992)
4. Q. Sung, D. Tsaan: J. Geol. Soc. China35, 389 (1992)
5. S. Xing-jue, N. Zhi-ran, X. He-ming: Acta Geophys.35, 71 (1992)