| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [be] essential to | 12 |
|
| 2 | [prep] [be] essential to | 12 |
|
| 3 | to [be] essential to | 12 |
|
| 4 | [prep] be essential to | 12 |
|
| 5 | [prep] be essential to | 12 |
|
