| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a long period [prep] | 216 |
|
| 2 | [vb past] a period [prep] | 80 |
|
| 3 | [vb past] long period [prep] | 9 |
|
| 4 | [vb past] a long period | 8 |
|
