| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [pron] is [adv] difficult maintain | 6 |
|
| 2 | [pron] [is] [adv] difficult to maintain | 6 |
|
| 3 | it [is] [adv] difficult maintain | 6 |
|
| 4 | [pron] [is] [adv] difficult maintain | 6 |
|
| 5 | [pers pn] [is] [adv] difficult maintain | 6 |
|
| 6 | it [is] [adv] difficult maintain | 6 |
|
