| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be a long period | 12 |
|
| 2 | [be] a long period | 7 |
|
| 3 | [be] a longer period | 5 |
|
| 4 | [was/were] a long period | 5 |
|
| 5 | was a long period | 5 |
|
