| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [num] [noun sg] [noun sg] period | 19 |
|
| 2 | [prep] a [num] month [noun] period | 8 |
|
| 3 | [prep] a [num] hour [noun] period | 5 |
|
| 4 | [prep] a two [noun sg] [noun] period | 5 |
|
