| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] [adv] a period of | 67 |
|
| 2 | [verb] [adv] a period of | 67 |
|
| 3 | [verb] [adv prt] a period of | 64 |
|
| 4 | [verb] over a period of | 59 |
|
| 5 | [verb] over a period of | 59 |
|
| 6 | [vb past] [adv] a period of | 23 |
|
| 7 | [v-ing] [adv] a period of | 12 |
|
| 8 | [vb -s] [adv] a period of | 9 |
|
| 9 | [to-vb] [adv] a period of | 6 |
|
| 10 | [vb pp] [adv] a period of | 6 |
|
| 11 | [vb base] [adv] a period of | 6 |
|
| 12 | [vb infin] [adv] a period of | 5 |
|
| 13 | occur [adv] a period of | 5 |
|
| 14 | extend [adv] a period of | 5 |
|
