| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a [adj] period [prep] time | 337 |
|
| 2 | for a [adj] period [prep] | 272 |
|
| 3 | for [adj] period [prep] time | 102 |
|
| 4 | for a period [prep] time | 33 |
|
