| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over a [adj] period of | 137 |
|
| 2 | [vb pp] over a [adj] period | 83 |
|
| 3 | [vb pp] over a period of | 70 |
|
| 4 | [vb pp] a [adj] period of | 15 |
|
