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drift and pillar
N. Staff. A system of working coal similar to the room and pillar system.
- 词性： noun
- 行业/领域： 采矿
- 类别 一般矿业; Mineral mining
- Government Agency: USBM
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创建者
- ed.young
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(V.I.P) 21084 分数 - 100% positive feedback
(Milwaukee, United States)
