Perhaps you should try some spelling variations:
"support migrants integration theories." » "support migrant integration theories.", "support immigrants integration theories.", "support migrants l'integration theories.", "support migrants integration theorems.", "support migrants integrationstheorie 2.", "support migrants integration theory.", "supporting migrants integration theories.", "support grant integration theories."
"supply race immigration policy." » "supply race migration policy.", "supply scale immigration policy.", "supply mass immigration policy.", "supply more immigration policy.", "supply rates immigration policy.", "supply reach immigration policy.", "supply case immigration policy."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("supply race immigration policy.") or ("support migrants integration theories."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("supply race immigration policy.") OR ("support migrants integration theories."))*.
• Removing quotes may allow a broader search: (( supply race immigration policy. ) or ( support migrants integration theories. ))*.