Perhaps you should try some spelling variations:
"international efforts economics series" » "international airports economics series", "international energy economics series", "international airport economics series", "international effects economics series", "international sports economic series", "international forest economics series"
"international open economy series" » "international hope economy series", "international order economy series", "international scope 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 open economy series") or ("international efforts economics series"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("international open economy series") OR ("international efforts economics series")).
• Removing quotes may allow a broader search: (( international open economy series ) or ( international efforts economics series )).
• Adding a wildcard symbol may retrieve word variants: (("international open economy series") or ("international efforts economics series"))*.