| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be required at [art] | 18 |
|
| 2 | [be] required at the | 12 |
|
| 3 | [is] required at [art] | 10 |
|
| 4 | is required at [art] | 10 |
|
| 5 | be required at [art] | 5 |
|
| 6 | [be] required at [art] | 5 |
|
