| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] a short period [prep] | 10 |
|
| 2 | [adv] a short period of | 9 |
|
| 3 | [adv] a short period of | 9 |
|
| 4 | only a short period [prep] | 7 |
|
