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| mode of sampling; type of sampling | |||
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抽样 方式 : 3 phrases in 2 subjects |
| Quality control and standards | 1 |
| Technology | 2 |
The server is undergoing maintenance and the site is working in read-only mode. Please check back later.">Add | The server is undergoing maintenance and the site is working in read-only mode. Please check back later.">Report an error
| Get short URL | Language Selection Tips