| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | at [adv] once a | 117 |
|
| 2 | [vb pp] at [adv] once | 54 |
|
| 3 | [vb pp] at [adv] a | 52 |
|
| 4 | [vb pp] [adv] once a | 18 |
|
