| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun prp] [prep] a period | 40 |
|
| 2 | [noun prp] for a period | 16 |
|
| 3 | [noun prp] over a period | 12 |
|
| 4 | [noun prp] after a period | 5 |
|
