| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have [verb] a period of | 21 |
|
| 2 | have [vb pp] a period of | 20 |
|
| 3 | has [verb] a period of | 8 |
|
| 4 | have entered a period of | 5 |
|
| 5 | have enter a period of | 5 |
|
| 6 | had [verb] a period of | 5 |
|
| 7 | have [verb] a period of | 5 |
|
