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 taxes integration theories."
"import trade integration series." » "import trade integration services.", "import trade interaction series.", "import trade integration server.", "export trade integration series.", "import price integration series.", "import taxes integration series."

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 series.") OR ("import trade integration theories."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"import trade integration series.\") OR (\"import trade integration theories.\"))".
• Removing quotes may allow a broader search: (( import trade integration series. ) OR ( import trade integration theories. )).
• Adding a wildcard symbol may retrieve word variants: (("import trade integration series.") OR ("import trade integration theories."))*.