| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a long period of | 140 |
|
| 2 | [prep] a long period of | 140 |
|
| 3 | over a long period of | 77 |
|
| 4 | for a long period of | 18 |
|
| 5 | after a long period of | 16 |
|
| 6 | of a long period of | 10 |
|
| 7 | to a long period of | 5 |
|
