| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | an [adv] [adj] period [prep] | 16 |
|
| 2 | an [adv] [adj] period [prep] | 14 |
|
| 3 | an [adv] [adj] period of | 7 |
|
| 4 | an [adv] short period [prep] | 5 |
|
