| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a period of [adv] twenty | 6 |
|
| 2 | [art] period of [adv] twenty | 6 |
|
| 3 | a period of [adv] twenty | 6 |
|
| 4 | [art] period of [adv] twenty | 6 |
|
| 5 | period of [adv] twenty [noun pl] | 5 |
|
| 6 | period of [adv] twenty [noun] | 5 |
|
| 7 | period of [adv] twenty year | 5 |
|
| 8 | period of [adv] twenty years | 5 |
|
