| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | at a [adj] period | 25 |
|
| 2 | at a [adj] period | 21 |
|
| 3 | at a particular period | 6 |
|
| 4 | at a particular period | 6 |
|
| 5 | at a critical period | 5 |
|
| 6 | at a critical period | 5 |
|
| 7 | at a period [adv] | 8 |
|
| 8 | at a period [prep] | 7 |
|
| 9 | at a period [Wh adv] | 7 |
|
| 10 | at a period [prep] | 7 |
|
| 11 | at a period when | 7 |
|
| 12 | at a period when | 7 |
|
| 13 | at a period of | 5 |
|
| 14 | at a period of | 5 |
|
