| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a long period of time | 98 |
|
| 2 | [prep] a long period [prep] time | 98 |
|
| 3 | [prep] a long period [prep] time | 98 |
|
| 4 | [prep] a long period [prep] time | 88 |
|
| 5 | over a long period [prep] time | 77 |
|
| 6 | over a long period [prep] time | 77 |
|
| 7 | for a long period [prep] time | 17 |
|
| 8 | for a long period [prep] time | 17 |
|
| 9 | [prep] a longer period [prep] time | 10 |
|
