| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [noun] | 430262 |
|
| 2 | [prep] [art] period | 5697 |
|
| 3 | [prep] [art] period | 5697 |
|
| 4 | [prep] a period | 2139 |
|
