| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adv] long period | 23 |
|
| 2 | [prep] a [adv] longer period | 21 |
|
| 3 | over a [adv] long period | 21 |
|
| 4 | for a [adv] long period | 19 |
|
| 5 | [prep] a much long period | 16 |
|
| 6 | [prep] a very long period | 8 |
|
