| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a [adv] short period [prep] | 44 |
|
| 2 | a [adv] short period of | 40 |
|
| 3 | a very short period [prep] | 19 |
|
| 4 | a relatively short period [prep] | 18 |
|
