Perhaps you should try some spelling variations:
"international policy economic surveys" » "international poverty economic surveys", "international prices economic surveys", "national policy economic surveys", "international policy economic studies", "international policy economic systems"
"international energy ecological services" » "international energy hydrological services", "international energy clinical services", "international energy meteorological services", "international energy technological services", "international early ecological services", "international energy psychological 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 policy economic surveys") or ("international energy ecological services"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("international policy economic surveys") OR ("international energy ecological services")).
• Removing quotes may allow a broader search: (( international policy economic surveys ) or ( international energy ecological services )).
• Adding a wildcard symbol may retrieve word variants: (("international policy economic surveys") or ("international energy ecological services"))*.