| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a period of | 1600 |
|
| 2 | [prep] a period of | 1600 |
|
| 3 | over a [noun] of | 1158 |
|
| 4 | over a [noun sg] of | 1133 |
|
| 5 | over [art] period of | 684 |
|
| 6 | over a period [prep] | 629 |
|
| 7 | over a period [prep] | 629 |
|
| 8 | over a period of | 618 |
|
| 9 | over a period of | 618 |
|
| 10 | over a period of | 618 |
|
