Perhaps you should try some spelling variations:
"import trade integration theories." » "import trade integration theorems.", "import trade integrationstheorie 2.", "import trade integration theory.", "export trade integration theories.", "import price integration theories.", "import share integration theories."
"import taxes integration efforts." » "import taxes international efforts.", "import taxes conservation efforts.", "import spaces integration efforts.", "import values integration efforts.", "import res integration efforts.", "export taxes integration efforts."

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

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