Perhaps you should try some spelling variations:
"international airport economics series" » "international transport economics series", "international airshow economics series", "international airports economic series", "international airline economics series"
"international shipping economy series" » "international shipping economic series", "international shipping economics series", "international sharing 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 shipping economy series") or ("international airport economics series"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("international shipping economy series") OR ("international airport economics series")).
• Removing quotes may allow a broader search: (( international shipping economy series ) or ( international airport economics series )).
• Adding a wildcard symbol may retrieve word variants: (("international shipping economy series") or ("international airport economics series"))*.