| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a period [prep] | 1753 |
|
| 2 | [vb past] a period [prep] | 80 |
|
| 3 | [vb past] [prep] a period | 62 |
|
| 4 | [vb past] [prep] a [prep] | 7 |
|
