Listak, Jeffrey M.
Longwall retreat of gate road pillars / by J.M. Listak and E.R. Bauer. - Washington, D.C. : U.S. Dept. of the Interior, Bureau of Mines, 1993. - 11 p. : ill. ; 28 cm. - Report of investigations ; 9444 . - Report of investigations (United States. Bureau of Mines) ; 9444. .
Includes bibliographical references (p. 11).
92023498
Ground control (Mining)--Pennsylvania.
Pillaring (Mining)
Longwall mining--Pennsylvania.
Gate roads (Mining)--Pennsylvania.
TN23 TN288 / .U43 no. 9444
622 s 622/.334
Longwall retreat of gate road pillars / by J.M. Listak and E.R. Bauer. - Washington, D.C. : U.S. Dept. of the Interior, Bureau of Mines, 1993. - 11 p. : ill. ; 28 cm. - Report of investigations ; 9444 . - Report of investigations (United States. Bureau of Mines) ; 9444. .
Includes bibliographical references (p. 11).
92023498
Ground control (Mining)--Pennsylvania.
Pillaring (Mining)
Longwall mining--Pennsylvania.
Gate roads (Mining)--Pennsylvania.
TN23 TN288 / .U43 no. 9444
622 s 622/.334