| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [to-vb] how [to-vb] and [vb infin] | 12 |
|
| 2 | [to-vb] how [verb] and [vb infin] | 12 |
|
| 3 | to learn how [verb] and [vb infin] | 8 |
|
