| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] [prep] a long period of | 15 |
|
| 2 | [adv] [prep] a long period of | 15 |
|
| 3 | [adv] [prep] a long period of | 12 |
|
| 4 | [adv] over a long period of | 8 |
|
