| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] [prep] a [det] year | 172 |
|
| 2 | period [prep] a [det] [noun] | 19 |
|
| 3 | period [prep] a [adj] year | 8 |
|
| 4 | period [prep] [art] [det] year | 6 |
|
