| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a period of | 2396 |
|
| 2 | a period in | 125 |
|
| 3 | a period during | 24 |
|
| 4 | a period for | 17 |
|
| 5 | a period at | 14 |
|
| 6 | a period after | 14 |
|
| 7 | a period from | 11 |
|
| 8 | a period as | 11 |
|
| 9 | a period between | 10 |
|
| 10 | a period with | 7 |
|
| 11 | a period before | 6 |
|
| 12 | a period to | 5 |
|
