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Risk of bias
| Reference | Random sequence generation | Allocation concealment | Blinding | Completeness of data |
|---|---|---|---|---|
| Eriksson and Granström8 | + | – | – | + |
| Salminen et al. 13 | + | + | – | + |
| Styrud et al. 9 | + | + | – | – |
| Svensson et al. 14 | + | + | – | + |
| Vons et al. 12 | + | + | – | – |
+, Low risk of bias; −, high risk of bias.
