| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be [prep] once [verb] | 45 |
|
| 2 | [be] at once [verb] | 41 |
|
| 3 | [be] [prep] once [vb pp] | 39 |
|
| 4 | [was/were] [prep] once [verb] | 34 |
|
| 5 | was [prep] once [verb] | 26 |
|
| 6 | were [prep] once [verb] | 8 |
|
| 7 | is [prep] once [verb] | 7 |
|
| 8 | [is] [prep] once [verb] | 7 |
|
| 9 | [be] [prep] once [v-ing] | 5 |
|
