| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period of | 544 |
|
| 2 | [prep] [adv] a [adj] of | 146 |
|
| 3 | [adv] a [adj] period of | 42 |
|
| 4 | [prep] [adv] a [adj] period | 27 |
|
