Beck, B. F., Pettit, A. J., & Herring, J. G. (1999). Hydrogeology and engineering geology of sinkholes and karst-1999: Proceedings og the seventh multidisciplinary conference on sinkholes and the engineering and environmental impacts of karst Harrisburg-Hershey, Pennsylvania, 10-14 April 1999. Rotterdam: A. A. Balkema.
Παραπομπή Chicago StyleBeck, Barry F., Arthur J. Pettit, and J. Gayle Herring. Hydrogeology and Engineering Geology of Sinkholes and Karst-1999: Proceedings Og the Seventh Multidisciplinary Conference On Sinkholes and the Engineering and Environmental Impacts of Karst Harrisburg-Hershey, Pennsylvania, 10-14 April 1999. Rotterdam: A. A. Balkema, 1999.
Παραπομπή MLABeck, Barry F., Arthur J. Pettit, and J. Gayle Herring. Hydrogeology and Engineering Geology of Sinkholes and Karst-1999: Proceedings Og the Seventh Multidisciplinary Conference On Sinkholes and the Engineering and Environmental Impacts of Karst Harrisburg-Hershey, Pennsylvania, 10-14 April 1999. Rotterdam: A. A. Balkema, 1999.