Perhaps you should try some spelling variations:
"supply national migration policies." » "supply national immigration policies.", "supply regional migration policies.", "supply national integration policies.", "supply national migration policy.", "supply national education policies."
"supply crowd integration theory." » "supply crowd integration through.", "supply crowd information theory.", "supply crowd integration report.", "supply grid integration theory.", "supply trade integration theory.", "supply chain integration theory.", "supply growth integration theory.", "supply cost integration theory.", "supply how integration theory."

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

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