Perhaps you should try some spelling variations:
"import policy intervention series." » "import policy interventions series.", "import policy intervention prices.", "import policy intervention systems.", "import policy intervention design.", "important policy intervention series.", "import price intervention series."
"import bans integration south." » "import bans integration study.", "import bans integration some.", "import bans integration through.", "import can integration south.", "import urban integration south.", "import data integration south.", "import taxes integration south."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("import bans integration south.") or ("import policy intervention series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("import bans integration south.") OR ("import policy intervention series."))*.
• Removing quotes may allow a broader search: (( import bans integration south. ) or ( import policy intervention series. ))*.