| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [adj] period of | 618 |
|
| 2 | [prep] a long [noun] of | 529 |
|
| 3 | [prep] a long [noun sg] of | 492 |
|
| 4 | [prep] a long period [prep] | 179 |
|
| 5 | [prep] a long period [prep] | 179 |
|
| 6 | [prep] [art] long period of | 168 |
|
| 7 | [prep] a long period of | 152 |
|
| 8 | [prep] a long period of | 152 |
|
