Waltham, T. (2008). "Sinkhole hazard case histories in karst terrains". Quarterly Journal of Engineering Geology and Hydrogeology. 41 (3): 291–300. doi:10.1144/1470-9236/07-211. S2CID128585380.
Waltham, T. (2008). "Sinkhole hazard case histories in karst terrains". Quarterly Journal of Engineering Geology and Hydrogeology. 41 (3): 291–300. doi:10.1144/1470-9236/07-211. S2CID128585380.