| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | happened [prep] [art] period [prep] | 6 |
|
| 2 | happened [prep] [art] period [prep] | 6 |
|
| 3 | happened [prep] [art] period of | 5 |
|
| 4 | happened [prep] [art] period of | 5 |
|
