| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] over a period of | 75 |
|
| 2 | [adv] over a period of | 34 |
|
| 3 | [adv] [verb] a period of | 22 |
|
| 4 | [adv] [verb] over a period | 8 |
|
