| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] to have been caused by | 23 |
|
| 2 | [vb pp] to have been caused [prep] | 17 |
|
| 3 | [vb past] to have been caused [prep] | 7 |
|
| 4 | thought to have been caused [prep] | 7 |
|
| 5 | think to have been caused [prep] | 7 |
|
| 6 | believe to have been caused [prep] | 6 |
|
