| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must have been [adv] | 576 |
|
| 2 | [modal v] have been as | 60 |
|
| 3 | must have [be] as | 10 |
|
| 4 | must have be as | 10 |
|
| 5 | must [verb] been as | 10 |
|
| 6 | must have [been] as | 10 |
|
