| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over a long period [prep] | 93 |
|
| 2 | [vb pp] over a period [prep] | 71 |
|
| 3 | [vb pp] over a long period | 44 |
|
| 4 | [vb pp] a long period [prep] | 9 |
|
