| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period [prep] | 736 |
|
| 2 | [noun pl] [prep] a period [prep] | 193 |
|
| 3 | [noun pl] [prep] a [adj] period | 183 |
|
| 4 | [noun pl] [prep] [adj] period [prep] | 49 |
|
| 5 | [noun pl] [prep] a [adj] [prep] | 27 |
|
