| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb pp] to be essential | 13 |
|
| 2 | seem to be essential | 7 |
|
| 3 | [vb past] to be essential | 6 |
|
| 4 | show to be essential | 5 |
|
| 5 | shown to be essential | 5 |
|
