| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] an indefinite period [prep] | 8 |
|
| 2 | [prep] an indefinite period [prep] | 8 |
|
| 3 | for an indefinite period [prep] | 6 |
|
| 4 | for an indefinite period [prep] | 6 |
|
| 5 | an indefinite period [prep] [noun] | 6 |
|
| 6 | an indefinite period [prep] [noun sg] | 6 |
|
