| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a longer period [prep] | 17 |
|
| 2 | [prep] a longer period of | 12 |
|
| 3 | [prep] a longer period of | 12 |
|
| 4 | over a longer period [prep] | 8 |
|
| 5 | for a longer period [prep] | 6 |
|
