| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [adj] period of | 208 |
|
| 2 | [prep] an [adj] period | 205 |
|
| 3 | an [adj] period of | 112 |
|
| 4 | [prep] an [adj] of | 17 |
|
