| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be once [prep] a | 13 |
|
| 2 | [be] once [prep] a | 13 |
|
| 3 | [was/were] once [prep] a | 10 |
|
| 4 | [be] once in a | 6 |
|
| 5 | was once [prep] a | 6 |
|
