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| 煤层; 煤的生成 | |||
| 含煤岩系 | |||
| coal formation: 34 phrases in 5 subjects |
| Desert science | 1 |
| Explosives and Explosive Ordnance Disposal | 10 |
| Metallurgy | 2 |
| Oil / petroleum | 2 |
| Technology | 19 |
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