| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | which have [been] used for | 22 |
|
| 2 | [Wh det] have been used for | 22 |
|
| 3 | [Wh det] had [been] used for | 10 |
|
| 4 | [Wh det] has [been] used for | 7 |
|
| 5 | [Wh det] have [been] used for | 5 |
|
