| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a certain [noun] of | 1598 |
|
| 2 | a certain [noun sg] of | 1594 |
|
| 3 | a [adj] period of | 954 |
|
| 4 | a certain period [prep] | 26 |
|
| 5 | a certain period [prep] | 26 |
|
| 6 | a certain period of | 22 |
|
| 7 | [art] certain period of | 22 |
|
| 8 | a certain period of | 22 |
|
