| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a [adv] long period [prep] | 14 |
|
| 2 | a [adv] long period of | 12 |
|
| 3 | a [adv] long period of | 12 |
|
| 4 | a very long period [prep] | 8 |
|
