| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over a long period of [noun] | 75 |
|
| 2 | over a long period [prep] [noun sg] | 74 |
|
| 3 | over a long period [prep] time | 71 |
|
| 4 | over a long period [prep] time | 71 |
|
