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Conrad, P. W., R. J. Sweigard, J. C. Yingling, D. H. Graves, and J. M. Ringe, “Use of Ripping to Alleviate Excessive Compaction on Reclaimed Surface Mined Land”, Transactions 2002, Vol. 312, Society for Mining, Metallurgy, and Exploration, Inc., Littleton, CO, 2002, pp. 159-165.