| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [art] fixed period [prep] | 30 |
|
| 2 | [prep] a fixed period [prep] | 29 |
|
| 3 | [prep] [art] fixed period of | 26 |
|
| 4 | for [art] fixed period [prep] | 18 |
|
| 5 | for [art] fixed period [prep] | 18 |
|
