Perhaps you should try some spelling variations:
"international prices economic theories" » "international prices economic theory", "international prices economics series", "international crises economic theories", "international prices econometric theories", "international services economic theories"
"national poverty economic surveys" » "national property economic surveys", "national forestry economic surveys", "national policy economic surveys", "national poverty economic studies", "national poverty economic systems"

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

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