| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adj] years [unc] duration | 71 |
|
| 2 | [adj] years ' duration | 71 |
|
| 3 | [adj] years ' duration | 71 |
|
| 4 | [adj] years ['s] duration | 71 |
|
| 5 | [num] years [unc] duration | 70 |
|
| 6 | four years [unc] duration | 27 |
|
| 7 | four years [unc] duration | 27 |
|
| 8 | three years [unc] duration | 25 |
|
| 9 | three years [unc] duration | 25 |
|
| 10 | two years [unc] duration | 7 |
|
| 11 | two years [unc] duration | 7 |
|
