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Year of publication, type of study and level of evidence.
| Authors [ref] | Year | Type of study | Level |
|---|---|---|---|
| De Boer et al. 16 | 2016 | Retrospective case control | III |
| Clark et al.7 | 2012 | Retrospective case control | III |
| Werner et al.17 | 2018 | Retrospective case control | III |
| Vourazeris et al.6 | 2016 | Retrospective case control | III |
| Friedman et al.18 | 2016 | Retrospective case control | III |
