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

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("international political economic studies") or ("international energy economic services"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("international political economic studies") OR ("international energy economic services")).
• Removing quotes may allow a broader search: (( international political economic studies ) or ( international energy economic services )).
• Adding a wildcard symbol may retrieve word variants: (("international political economic studies") or ("international energy economic services"))*.