| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] [verb] a [adj] period of | 16 |
|
| 2 | [adv] [vb past] a [adj] period [prep] | 7 |
|
| 3 | [adv] [verb] a long period [prep] | 5 |
|
| 4 | [adv] [vb infin] a [adj] period [prep] | 5 |
|
