| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] [pron] [adv] difficult maintain | 6 |
|
| 2 | make [pron] [adv] difficult maintain | 5 |
|
| 3 | [pron] [be] [adv] difficult maintain | 7 |
|
| 4 | [pron] be [adv] difficult maintain | 7 |
|
| 5 | [pron] [is] [adv] difficult maintain | 6 |
|
| 6 | [pron] is [adv] difficult maintain | 6 |
|
| 7 | [pron] [adv] difficult maintain [art] | 5 |
|
| 8 | [pron] [adv] difficult maintain [art] | 5 |
|
