| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb mod] have been caused [prep] | 47 |
|
| 2 | [modal v] have been caused [prep] | 47 |
|
| 3 | [modal v] have been caused by | 42 |
|
| 4 | may have been caused [prep] | 19 |
|
| 5 | may have been caused [prep] | 19 |
|
| 6 | could have been caused [prep] | 13 |
|
| 7 | could have been caused [prep] | 13 |
|
| 8 | might have been caused [prep] | 9 |
|
| 9 | might have been caused [prep] | 9 |
|
