| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun pl] have been used | 267 |
|
| 2 | [noun pl] had been used | 56 |
|
| 3 | [noun pl] has been used | 24 |
|
| 4 | methods have been used | 15 |
|
| 5 | techniques have been used | 15 |
|
| 6 | materials have been used | 5 |
|
| 7 | resources have been used | 5 |
|
