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

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 series") OR ("national poverty economic studies"))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"international prices economic series\") OR (\"national poverty economic studies\"))".
• Removing quotes may allow a broader search: (( international prices economic series ) OR ( national poverty economic studies )).
• Adding a wildcard symbol may retrieve word variants: (("international prices economic series") OR ("national poverty economic studies"))*.