| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] over a [adj] period [prep] | 12 |
|
| 2 | [adv] over a [adj] period of | 10 |
|
| 3 | [adv] over a long period [prep] | 8 |
|
| 4 | [adv] over a long period [prep] | 8 |
|
