| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] [prep] a period of | 652 |
|
| 2 | and [prep] a period of | 23 |
|
| 3 | [noun] and [prep] a period | 17 |
|
| 4 | [noun] and a period of | 10 |
|
