| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | must be [verb] | 12065 |
|
| 2 | must be [vb pp] | 11027 |
|
| 3 | [vb mod] be referred | 298 |
|
| 4 | [modal v] be referred | 298 |
|
| 5 | must be refer | 26 |
|
| 6 | must [be] referred | 22 |
|
| 7 | must be referred | 22 |
|
| 8 | must [be] referred | 22 |
|
| 9 | must be referred | 22 |
|
