| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] over a period of [noun pl] | 17 |
|
| 2 | [adv] over a period [prep] [noun pl] | 17 |
|
| 3 | [adv] over a period of [noun pl] | 17 |
|
| 4 | [adv] over a period [prep] [noun pl] | 9 |
|
| 5 | [adv prt] over a period [prep] [noun pl] | 8 |
|
| 6 | [adv] over a period [prep] years | 7 |
|
| 7 | [adv] over a period [prep] weeks | 5 |
|
