| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be [verb] [prep] a period [prep] | 57 |
|
| 2 | be [vb pp] [prep] a period [prep] | 54 |
|
| 3 | be [verb] [prep] a period of | 52 |
|
| 4 | be [verb] over a period [prep] | 15 |
|
| 5 | be [verb] for a period [prep] | 13 |
|
| 6 | be [verb] within a period [prep] | 10 |
|
| 7 | be [verb] by a period [prep] | 5 |
|
| 8 | be [verb] as a period [prep] | 5 |
|
