| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a [adj] period [prep] [noun] | 675 |
|
| 2 | over a period [prep] [noun] | 296 |
|
| 3 | over a [adj] period [prep] | 176 |
|
| 4 | over [adj] period [prep] [noun] | 8 |
|
