| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] must be [verb] by reference | 6 |
|
| 2 | [noun sg] must be [verb] by reference | 6 |
|
| 3 | must be [verb] by reference [prep] | 10 |
|
| 4 | must be [verb] by reference to | 10 |
|
| 5 | must be [verb] by reference to | 10 |
|
| 6 | must be [verb] by reference [prep] | 10 |
|
