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ventilation system : 33 phrases in 13 subjects |
Coal | 6 |
Construction | 8 |
Earth sciences | 1 |
General | 4 |
Industry | 1 |
Medical | 1 |
Metallurgy | 1 |
Mining | 2 |
Municipal planning | 2 |
Natural resourses and wildlife conservation | 2 |
Non-governmental organizations | 1 |
Technology | 2 |
Transport | 2 |