| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [to-vb] [adv] [prep] a [adj] period | 8 |
|
| 2 | [to-vb] [adv] [prep] a [adj] period | 8 |
|
| 3 | [to-vb] [adv] for a [adj] period | 5 |
|
| 4 | [to-vb] [adv] for a [adj] period | 5 |
|
