| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period [prep] | 871 |
|
| 2 | [prep] a [adj] period [prep] | 871 |
|
| 3 | over a [adj] [noun] [prep] | 540 |
|
| 4 | over [art] [adj] period [prep] | 234 |
|
| 5 | over a [adj] period [prep] | 183 |
|
| 6 | over a [adj] period [prep] | 183 |
|
