| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a long period than | 12 |
|
| 2 | [prep] a long period than | 12 |
|
| 3 | [prep] a long period than | 12 |
|
| 4 | [prep] a longer period than | 12 |
|
| 5 | for a long period than | 7 |
|
| 6 | for a long period than | 7 |
|
