What is Russia's greatest source of wealth?

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Tags

1. #accounted
2. #exports
3. #energy
4. #share
5. #revenues
6. #total
7. #russia
8. #budget
9. #sector
10. #major
11. #drive
12. #abundance
13. #federal
14. #growth
15. #metals
16. #precious
17. #natural
18. #relies
19. #which