| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | studies have been | 140 |
|
| 2 | studies [vb base] been | 111 |
|
| 3 | studies have been | 111 |
|
| 4 | studies has been | 17 |
|
| 5 | studies [vb -s] been | 17 |
|
| 6 | studies had been | 11 |
|
| 7 | studies [vb past] been | 11 |
|
