| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] [adv] a period of | 67 |
|
| 2 | [verb] [adv] a long period | 31 |
|
| 3 | [verb] a long period of | 16 |
|
| 4 | [adv] a long period of | 12 |
|
