Perhaps you should try some spelling variations:
"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."
"import trade integration theory." » "import trade integration through.", "import trade information theory.", "import trade innovation theory.", "export trade integration theory.", "import price integration theory.", "import share 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: (("import trade integration theory.") or ("import taxes integration efforts."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("import trade integration theory.") OR ("import taxes integration efforts.")).
• Removing quotes may allow a broader search: (( import trade integration theory. ) or ( import taxes integration efforts. )).
• Adding a wildcard symbol may retrieve word variants: (("import trade integration theory.") or ("import taxes integration efforts."))*.