Perhaps you should try some spelling variations:
"international poverty economic surveys" » "national poverty economic surveys", "international property economic surveys", "international forestry economic surveys", "international policy economic surveys", "international poverty economic studies", "international poverty economic systems"
"national polish economy series" » "national policy economy series", "national police economy series", "national post economy series", "national polish economic series", "national spanish economy series", "national politics economy series", "national polish economics series"

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

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