| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb mod] have [been] used for | 15 |
|
| 2 | [modal v] have [been] used for | 15 |
|
| 3 | [modal v] have been used for | 15 |
|
| 4 | could have [been] used for | 6 |
|
| 5 | could have [been] used for | 6 |
|
| 6 | may have [been] used for | 5 |
|
| 7 | may have [been] used for | 5 |
|
