| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a very long period | 8 |
|
| 2 | [prep] a very long period | 8 |
|
| 3 | a very long period [prep] | 8 |
|
| 4 | a very long period [prep] | 8 |
|
| 5 | a very long period of | 7 |
|
| 6 | a very long period of | 7 |
|
