Perhaps you should try some spelling variations:
"airports vertical integration series." » "airports regional integration series.", "airports vertical integration theories.", "airports vertical integrating services.", "airports vertical integration schemes.", "airport terminal integration series."
"support system integration series." » "support system integration theories.", "support system integrating services.", "support system integration schemes.", "support systems integration series.", "support sector integration series.", "supply system integration series."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("airports vertical integration series.") or ("support system integration series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("airports vertical integration series.") OR ("support system integration series.")).
• Removing quotes may allow a broader search: (( airports vertical integration series. ) or ( support system integration series. )).
• Adding a wildcard symbol may retrieve word variants: (("airports vertical integration series.") or ("support system integration series."))*.