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2. Todd, ., Groundwater Hydrology, John Wiley, 1959, 336 pp.
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4. Coal Mine Regulations-Precautions against inrushes, 1979, U.K.
5. Babcock, C. O. and Hocker, V. E., Results of Research to Develop Guidelines for Mining Near-Surface and Underground Bodies of Water, Dept. of Interior, USBM Report K 8741, 17 p, 1977.