| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | may once have [be] | 14 |
|
| 2 | may once [vb infin] be | 14 |
|
| 3 | may once [vb infin] [been] | 14 |
|
| 4 | may once [vb infin] been | 14 |
|
| 5 | may once [vb infin] [be] | 14 |
|
