| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] [prep] a period of | 87 |
|
| 2 | [prep] a short period of | 61 |
|
| 3 | [adv] [prep] a short period | 25 |
|
| 4 | [adv] a short period of | 9 |
|
