Perhaps you should try some spelling variations:
"import duties integration theories." » "import duties integration theorems.", "import duties integrationstheorie 2.", "import duties integration theory.", "import studies integration theories.", "import dis integration theories.", "import dutch integration theories.", "imports duties integration theories."
"supply factor integration series." » "supply facto integration series.", "supply sector integration series.", "supply actor interaction series.", "supply factor integration services.", "supply factor interaction series.", "supply factor integration server.", "supply factors integration series."

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("import duties integration theories.") OR ("supply factor integration series."))~.
• Removing quotes may allow a broader search: (( import duties integration theories. ) or ( supply factor integration series. ))~.
• Adding a wildcard symbol may retrieve word variants: (("import duties integration theories.") or ("supply factor integration series."))*.