| Answer | Crossword Clue |
|---|---|
| OSAGE | 500-mile tributary of the Missouri. |
| SURA | 500-mile tributary of the Volga. |
| SURA | 500-mile tributary to the Volga. |
| SURA | 500-mile tributary of Volga. |
| SURA | 500-mile river, tributary of Volga. |
| PRUT | 500-mile Danube tributary, crossed by Reds. |
