| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a period [prep] a | 63 |
|
| 2 | a period of a | 45 |
|
| 3 | a period in a | 9 |
|
| 4 | a period as a | 7 |
|
| 5 | a period [prep] an | 7 |
|
