Table 1. Studies' design.
| Studies | Comparative studies | Descriptive studies | Prospective studies | Retrospective studies |
| References | 6-8,10,12-18,27-28,35,37-40,45,53-54 | 9,11,19-26,34,36,41-44,46-52 | 7-8,10,18-22,27,35 | 12-14,43 |
| No. of studies | 21 | 23 | 10 | 4 |
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