| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period of | 544 |
|
| 2 | [prep] such a [adj] period | 26 |
|
| 3 | such a [adj] period of | 10 |
|
| 4 | [prep] such a period of | 8 |
|
