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