| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a period of time [verb] | 14 |
|
| 2 | [prep] a period [prep] time [verb] | 14 |
|
| 3 | [prep] a period [prep] time [verb] | 14 |
|
| 4 | over a period [prep] time [verb] | 9 |
|
| 5 | over a period [prep] time [verb] | 9 |
|
| 6 | [prep] a period [prep] time [to-vb] | 6 |
|
