| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] over [art] period of | 40 |
|
| 2 | [adv] over a period [prep] | 34 |
|
| 3 | [adv] over the period [prep] | 8 |
|
| 4 | gradually over [art] period [prep] | 7 |
|
