| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb infin] a [adj] period [prep] | 18 |
|
| 2 | [vb infin] a [adj] period of | 15 |
|
| 3 | [vb infin] a [adj] period of | 15 |
|
| 4 | [vb infin] a [adj] period [prep] | 14 |
|
