| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [art] once in a | 20 |
|
| 2 | [art] once in a | 20 |
|
| 3 | [art] once [prep] a | 20 |
|
| 4 | [art] once [prep] a | 20 |
|
| 5 | a once [prep] a | 11 |
|
| 6 | every once [prep] a | 9 |
|
