| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | by refer to [art] | 57 |
|
| 2 | by refer [prep] [art] | 57 |
|
| 3 | by referring [prep] [art] | 57 |
|
| 4 | by refer [prep] the | 42 |
|
| 5 | by refer [prep] a | 13 |
|
