| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a short period [prep] | 126 |
|
| 2 | a short period of | 84 |
|
| 3 | a short period of | 84 |
|
| 4 | a short period in | 13 |
|
| 5 | a short period in | 13 |
|
