| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a fixed period | 52 |
|
| 2 | [prep] a fixed period | 52 |
|
| 3 | for a fixed period | 35 |
|
| 4 | for a fixed period | 35 |
|
| 5 | a fixed period [prep] | 33 |
|
| 6 | a fixed period [prep] | 33 |
|
| 7 | a fixed period of | 27 |
|
| 8 | a fixed period of | 27 |
|
