| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | difficulty [prep] [v-ing] [conj] a | 8 |
|
| 2 | difficulty [prep] [verb] [conj] a | 8 |
|
| 3 | difficulty of [verb] [conj] a | 6 |
|
| 4 | difficulty of [verb] [conj] a | 6 |
|
| 5 | difficulty [prep] [verb] [subord] a | 5 |
|
