1. Bell M, Limbrey S (1982) Archaeological aspects of woodland ecology. Bar Int Ser 146:115–127
2. Caramanna G, Ciotoli G, Nisio S (2008) A review of natural sinkhole phenomena in Italian plain areas. Nat Hazards 45:145–172
3. Che YT, Yu JZ (1985) Karst in China. Science Press, Beijing, China
4. Chen ZJ (1959) Structure mechanics of clay. Sci China 8(1):41–45
5. Chen DY (1993) Study on the micro-mechanism m of rheological and creep model and the engineering calculation. Ph.D. thesis, Civil Engineering, Tongji University, China