| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [det] [be] a period of | 14 |
|
| 2 | [det] be a period of | 14 |
|
| 3 | this [be] a period of | 14 |
|
| 4 | [det] was a period of | 10 |
|
| 5 | [det] [was/were] a period of | 10 |
|
