Perhaps you should try some spelling variations:
"international political economic series" » "international policy economic series", "international political economy series", "international ecological economics series", "international political economics series", "international political economic services"
"international energy economic studies" » "international energy economic status", "international energy economics studies", "international energy economy studies", "international ecology economic studies"

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("international political economic series") or ("international energy economic studies"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("international political economic series") OR ("international energy economic studies")).
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