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| Author | Allocation concealment | Follow up | Total (Max‐3) |
| Cooper 1980 | 1 | 0 | 1 |
| Cooper 1981 | 1 | 0 | 1 |
| Cooper 1988 | 1 | 0 | 1 |
| Cooper 1998 | 1 | 1 | 2 |
| Dionne 1994 | 1 | 0 | 1 |
| Dolci 1994 | 1 | 0 | 1 |
| Forbes 1984b | 2 | 0 | 2 |
| Forbes 1989 | 1 | 0 | 1 |
| Forbes 1990 | 2 | 0 | 2 |
| Hersh 2000 | 1 | 1 | 2 |
| Kiersch 1994 | 1 | 1 | 2 |
| Kubitzek 2003 | 1 | 1 | 2 |
| Lehnert 1990 | 1 | 1 | 2 |
| Mehlisch 1995 | 2 | 1 | 3 |
| Moller 2000 | 1 | 1 | 2 |
| Olson 2001 | 2 | 1 | 3 |
| Seymour 1996 | 1 | 1 | 2 |
| Seymour 2003 | 2 | 0 | 2 |
| Skoglund 1991 | 2 | 0 | 2 |
| Sunshine 1986 | 2 | 1 | 3 |
| Vattaraphudej 1986 | 1 | 1 | 2 |
