| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a short period [prep] | 126 |
|
| 2 | [adv] a period [prep] | 117 |
|
| 3 | [adv] short period [prep] | 62 |
|
| 4 | [adv] a short period | 22 |
|
