Perhaps you should try some spelling variations:
"import taxes integration theories." » "import taxes integration theory.", "import taxes integration through.", "import taxes integration efforts.", "import trade integration theories.", "import fare integration theories.", "import care integration theories.", "export taxes integration theories."
"export prices integrating services." » "export prices integrated services.", "export prices testing services.", "export prices integrating policies.", "export policies integrating services.", "export prices international services.", "export services integration services.", "import prices integrating services."

Try widening your search to All Fields.

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

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