| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have been an [adj] factor | 15 |
|
| 2 | have [been] an important factor | 10 |
|
| 3 | has [been] an [adj] factor | 5 |
|
| 4 | had [been] an [adj] factor | 5 |
|
