| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] a brief period [prep] | 17 |
|
| 2 | [verb] a brief period of | 15 |
|
| 3 | [vb past] a brief period [prep] | 9 |
|
| 4 | [v-ing] a brief period [prep] | 5 |
|
