| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over a period of [noun sg] [prep] | 11 |
|
| 2 | over a period of [noun sg] [prep] | 11 |
|
| 3 | over a period [prep] [noun sg] [prep] | 11 |
|
| 4 | over a period [prep] time [prep] | 11 |
|
