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Quality measures of the included studies.
| Study | M1 | M2 | M3 | M4 | M5 | M Score |
|---|---|---|---|---|---|---|
| Da MF, 2008 | 1 | 1 | 0 | 1 | 1 | 4 |
| Ji ZJ, 2009 | 1 | 1 | 0 | 1 | 1 | 4 |
| Li Y, 2010 | 1 | 1 | 0 | 1 | 0 | 3 |
| Liao JQ, 2006 | 1 | 1 | 0 | 1 | 1 | 4 |
| Liu YJ, 2009 | 1 | 1 | 0 | 1 | 1 | 4 |
| Luo B, 2007 | 1 | 0 | 0 | 1 | 1 | 3 |
| Sun DN, 2007 | 1 | 1 | 0 | 1 | 0 | 3 |
| Wang QZ, 2008 | 1 | 1 | 0 | 1 | 1 | 4 |
| Wang XY, 2008 | 1 | 1 | 0 | 1 | 1 | 4 |
| Yang JX, 2008 | 1 | 1 | 0 | 1 | 0 | 3 |
| Yao MJ, 2009 | 1 | 1 | 0 | 1 | 0 | 3 |
