| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | once [prep] a | 498 |
|
| 2 | once [prep] a | 474 |
|
| 3 | once in a | 205 |
|
| 4 | once upon a | 163 |
|
| 5 | once [prep] an | 24 |
|
| 6 | once as a | 20 |
|
| 7 | once on a | 19 |
|
| 8 | once with a | 17 |
|
| 9 | once by a | 15 |
|
| 10 | once to a | 10 |
|
| 11 | once at a | 7 |
|
| 12 | once into a | 7 |
|
| 13 | once for a | 7 |
|
| 14 | once during a | 5 |
|
| 15 | once from a | 5 |
|
