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50 (L) — 1939-1940
U.S. Accident Rate, 199.
U.S. Explosions and Fires, 246.
U.S. Mine Labour, 213.
U.S. Mineral Values, 296.
U.S. Mining Explosives, 203.
U.S. Rock Dusting, 384.
U.S. Safety Trophies, 117.
U.S. Timbering Regulations, 149.
U.S. Wet Drilling, 341.
Underground Fires, 14, 218, 234, 241, 247, 266.
Underground Transport, 162.
Upcast Shaft, Closing, 336.
Use of Discarded Plant, 135.
Use Urged, Steel Props, 181.
Utilisation, Coal, 250.
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