| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | an [adj] period [prep] | 151 |
|
| 2 | in [adj] period [prep] | 86 |
|
| 3 | in an [adj] period | 11 |
|
| 4 | in an [adj] [prep] | 7 |
|
