1. Che Y T, Yu J Z, Liu W Z. 1999. The forming and evolvement mechanism of precursor in ground fluid before three strong earthquakes in Huabei district. Earthquake Research in China, 15(2): 139–150 (in Chinese)
2. First Division of Center for Analysis and Prediction, State Seismological Bureau. 1984. The Picture Collection of Chinese Earthquake Precursor (1962–1980). Beijing: Seismological Press, 17–18 (in Chinese)
3. Guo Z J. 1964. The change of ground water level before earthquake occurrence. Acta Geophysica Sinica, 13(3): 223–226 (in Chinese)
4. Liu Y W, Zhang Y S. 1998. Dynamic evolution characteristics precursory of ground fluid before Gonghe earthquake of M s7.0. Northwestern Seismological Journal, 20(1): 59–64 (in Chinese)
5. Liu Y W, Fan S H, Cao L L. 1999. Relationship between the medium-short term anomalies of ground fluid and the seismicity parameter. Earthquake, 19(1): 19–25 (in Chinese)