| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | has occurred | 561 |
|
| 2 | had occurred | 389 |
|
| 3 | have occurred | 278 |
|
| 4 | have occurred | 260 |
|
| 5 | to have occurred | 112 |
|
| 6 | having occurred | 20 |
|
