| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be a period of | 156 |
|
| 2 | was a period [prep] | 75 |
|
| 3 | is a period [prep] | 35 |
|
| 4 | be a period [prep] | 33 |
|
| 5 | were a period [prep] | 14 |
|
| 6 | be a period in | 13 |
|
| 7 | been a period [prep] | 13 |
|
| 8 | be a period during | 6 |
|
| 9 | 's a period [prep] | 6 |
|
