| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [is] [to-vb] [adj] [noun] | 1520 |
|
| 2 | difficult [to-vb] [adj] [noun] | 456 |
|
| 3 | [is] difficult [to-vb] [adj] | 211 |
|
| 4 | [is] difficult [to-vb] [noun] | 142 |
|
