| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] a long period of | 16 |
|
| 2 | [verb] a long period of | 11 |
|
| 3 | [vb pp] a long period of | 5 |
|
| 4 | [verb] a longer period of | 5 |
|
