| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over a [adj] period of | 143 |
|
| 2 | [adv] over a period of | 60 |
|
| 3 | [adv] a [adj] period of | 45 |
|
| 4 | [adv] over a [adj] period | 44 |
|
