| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] [verb] [prep] a period [prep] | 38 |
|
| 2 | [adv] [verb] [prep] a period of | 34 |
|
| 3 | [adv] [vb pp] [prep] a period [prep] | 28 |
|
| 4 | [adv] [verb] over a period [prep] | 8 |
|
| 5 | [adv] [verb] over a period [prep] | 8 |
|
| 6 | [adv] [verb] for a period [prep] | 7 |
|
| 7 | [adv] [verb] for a period [prep] | 7 |
|
