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