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02h0057711 20140617080953.0 s1956 dcuab fr |000|||eng | CNY200.00 NGL a713 ; a873.1 Hartley, John C. Anthracite mechanical-mining investigations : use of yielding steel supports (props) in combination with backfilling for mining thick, flat beds / by John C. Hartley, John D. Cooner, Robert J. Brennan. Washington, D.C. : U.S. Dept. of the Interior, Bureau of Mines, 1956. ii, 29 p. : ill., maps ; 28 cm. Report of investigations (United States. Bureau of Mines) ; 5290 Coal-mining machinery. ; Anthracite coal industry. aBrennan, Robert J. ; aCooner, John D. Report of investigations (United States. Bureau of Mines) ; 5290. aCN bNGL 010001 P 720.66 R29u v5290 ; rCNY200.00 ; h1 whx011