| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have been [verb] [prep] [adj] research | 12 |
|
| 2 | [vb base] been [vb pp] [prep] [adj] research | 12 |
|
| 3 | [vb base] been [verb] by [adj] research | 6 |
|
