| Study | Reason for exclusion |
|---|---|
| Andreev 1992 | Not a randomized controlled trial |
| Cafiero 1994 | Not a randomized controlled trial |
| Chiandussi 1991 | Not a randomized controlled trial |
| Divitiis 1986 | Not a randomized controlled trial |
| Golikov 1993 | Not a randomized controlled trial |
| Grazioli 1989 | Not a randomized controlled trial |
| Montanari 1981 | Not a randomized controlled trial |
| Nedoshivin 1996 | Not a randomized controlled trial |
| Perepech 1993 | Not a randomized controlled trial |
| Perepech 1997 | Not a randomized controlled trial |
| Perepech 2001 | Not a randomized controlled trial |
| Reimers 1994 | Not a randomized controlled trial |
| Stejfa 1993 | Not a randomized controlled trial |
| Tomaszewski 1994 | Not a randomized controlled trial |
| Weber 1995 | Not a randomized controlled trial |
| Weinbergova 1996 | Not a randomized controlled trial |
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