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Quality of articles assessed using a framework for assessing internal validity [26]
| Author | High 12 or more | Moderate 10-11 | Low 9 or less |
|---|---|---|---|
| Bhattacharyya (2007) [14] | ✓ | ||
| Brink (2008) [30] | ✓ | ||
| Fukuoka (2009) [28] | ✓ | ||
| Engblom (1994) [27] | ✓ | ||
| Ladwig (1994) [34] | ✓ | ||
| Mayou (2000) [9] | ✓ | ||
| McGee (2006) [35] | ✓ | ||
| Mittag (2001) [33] | ✓ | ||
| Soderman (2003) [5] | ✓ | ||
| Soejima (1999) [31] | ✓ | ||
| Sykes (2000) [32] | ✓ | ||
| Samkange-Zeeb (2006) [29] | ✓ | ||
