| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] [prep] a period [prep] | 418 |
|
| 2 | [prep] a long period [prep] | 162 |
|
| 3 | [verb] [prep] a long period | 72 |
|
| 4 | [verb] a long period [prep] | 19 |
|
