| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period of | 584 |
|
| 2 | and [prep] a [adj] period | 24 |
|
| 3 | and [prep] a period of | 23 |
|
| 4 | and a [adj] period of | 8 |
|
