| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] [adj] years [unc] | 817 |
|
| 2 | [prep] [num] years [unc] | 762 |
|
| 3 | [prep] 15 [noun] [unc] | 31 |
|
| 4 | [prep] 15 [noun pl] [unc] | 28 |
|
| 5 | [prep] 15 years [unc] | 22 |
|
| 6 | [prep] 15 year [unc] | 22 |
|
