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1
Degasification study from an air shaft in the Beckley coalbed
“…United States. Bureau of Mines…”
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Government Document Online Book -
2
Comparisons between cross-measure boreholes and surface gob holes
“…United States. Bureau of Mines…”
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Government Document Online Book -
3
Horizontal trajectories of rotary-drilled holes
“…United States. Bureau of Mines…”
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Government Document Online Book