| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | studies have [been] | 140 |
|
| 2 | studies have been | 140 |
|
| 3 | studies have be | 140 |
|
| 4 | studies have [be] | 111 |
|
| 5 | studies has [be] | 17 |
|
| 6 | studies had [be] | 11 |
|
