| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be [vb pp] over a long period | 14 |
|
| 2 | be [vb pp] over a long period | 10 |
|
| 3 | be [vb pp] over a longer period | 8 |
|
| 4 | been [vb pp] over a long period | 5 |
|
