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Impact factors of studies included in the meta-analysis
| Study | Year | Impact factor |
|---|---|---|
| Chen [33] | 2013 | 2.857 |
| Chen [16] | 2010 | 3.392 |
| Chen [23] | 2011 | 3.168 |
| Cui [34] | 2013 | 3.168 |
| Gu [27] | 2012 | 4.12 |
| He [24] | 2011 | 2.464 |
| Jain [28] | 2012 | 5.935 |
| Lan [35] | 2013 | 3.677 |
| Liao [36] | 2013 | 3.066 |
| Liu [25] | 2011 | 2.406 |
| Liu [29] | 2012 | 3.382 |
| Lv [26] | 2011 | 3.73 |
| Wang [37] | 2013 | 3.637 |
| Wu [30] | 2012 | 3.73 |
| Zhang [31] | 2012 | 1.271 |
| Zhang [17] | 2009 | 9.858 |
| Zhuang [32] | 2012 | 12.821 |
| Xu [51] | 2014 | 1.879 |
| Lu [52] | 2013 | 3.463 |
| Mean value | 4.107 |
