Perhaps you should try some spelling variations:
vertical integration » regional integration
interactions series » interaction terms, interactions between
integration series » integration theories, integrating services, integration schemes
state interactions » state interventions, face interactions, strategic interactions
airports vertical » airport terminal
support state » support staff, support strategy, support estimate

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 state interactions series. ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( airports vertical integration series. ) OR ( support state interactions series. )).
• Adding a wildcard symbol may retrieve word variants: (( airports vertical integration series. ) or ( support state interactions series. ))*.