| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over a [adj] period of | 137 |
|
| 2 | [verb] a [adj] period of | 135 |
|
| 3 | [verb] over a [adj] period | 86 |
|
| 4 | [verb] over a period of | 75 |
|
