| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] [prep] a period of time | 31 |
|
| 2 | [adv] over a period of time | 22 |
|
| 3 | [adv prt] [prep] a period of time | 15 |
|
| 4 | [adv] [prep] a period of time | 15 |
|
| 5 | up [prep] a period of time | 5 |
|
| 6 | up [prep] a period of time | 5 |
|
| 7 | [adv] for a period of time | 5 |
|
