| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [pers pn] [vb -s] been necessary for | 5 |
|
| 2 | [pers pn] has [been] necessary for | 5 |
|
| 3 | [pers pn] [vb -s] [been] necessary for | 5 |
|
| 4 | it [vb -s] [been] necessary for | 5 |
|
