| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb past] [adv] a period of time | 7 |
|
| 2 | [vb past] [adv] a period [prep] time | 7 |
|
| 3 | [vb past] [adv] a period of time | 7 |
|
| 4 | [vb past] over a period [prep] time | 6 |
|
| 5 | [vb past] [adv prt] a period [prep] time | 6 |
|
| 6 | [vb past] over a period [prep] time | 6 |
|
