| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period | 1796 |
|
| 2 | [prep] a [adj] year | 891 |
|
| 3 | a [adj] year period | 130 |
|
| 4 | [prep] [adj] year period | 6 |
|
