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| 分层设色法 | |||
| 层系 | |||
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layer system : 18 phrases in 10 subjects |
| Air defense | 1 |
| Aviation | 2 |
| China | 1 |
| Earth sciences | 2 |
| Electronics | 3 |
| General | 1 |
| Metallurgy | 2 |
| Space | 1 |
| Technology | 3 |
| Wind Energy | 2 |
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