| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] an [adv] [adj] period [prep] | 9 |
|
| 2 | [prep] an [adv] [adj] period [prep] | 9 |
|
| 3 | an [adv] [adj] period [prep] [noun] | 7 |
|
| 4 | an [adv] [adj] period [prep] [noun sg] | 6 |
|
