| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | may [adv] have been | 768 |
|
| 2 | may [adv] have been | 520 |
|
| 3 | [vb mod] once have been | 67 |
|
| 4 | [modal v] once have been | 67 |
|
| 5 | may once have be | 14 |
|
| 6 | may once have been | 14 |
|
| 7 | may once [vb infin] been | 14 |
|
| 8 | may once have been | 14 |
|
| 9 | may once have [been] | 14 |
|
| 10 | may once [verb] been | 14 |
|
| 11 | may once have [be] | 14 |
|
| 12 | may once have been | 14 |
|
