| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | and [prep] a period of | 23 |
|
| 2 | and [prep] a period of | 23 |
|
| 3 | and over a period of | 12 |
|
| 4 | and for a period of | 6 |
|
| 5 | and after a period of | 5 |
|
