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

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