| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | period [prep] a [adj] years | 8 |
|
| 2 | period [prep] a [adj] years | 8 |
|
| 3 | period of a [adj] years | 7 |
|
| 4 | period of a [adj] years | 7 |
|
| 5 | period [prep] a [det] years | 6 |
|
| 6 | period [prep] a few years | 6 |
|
| 7 | period [prep] a few years | 6 |
|
