| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] [adv] a period of | 67 |
|
| 2 | [verb] for a period of | 62 |
|
| 3 | [adv] for a period of | 23 |
|
| 4 | [verb] [adv] for a period | 20 |
|
