Perhaps you should try some spelling variations:
"improving basic performance series." » "improving basic performance metrics.", "improving basic performance reviews.", "improving basic performance review.", "improving bank performance series.", "improving past performance series.", "improving seismic performance series.", "improving air performance series.", "improve basic performance series.", "improving public performance series."
"improving based performance based." » "improving bank performance based.", "improving care performance based.", "improving board performance based.", "improving based performance measures.", "improving shared performance based.", "improving water performance based.", "improving land performance based."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving basic performance series.") OR ("improving based performance based."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"improving basic performance series.\") OR (\"improving based performance based.\"))".
• Removing quotes may allow a broader search: (( improving basic performance series. ) OR ( improving based performance based. )).
• Adding a wildcard symbol may retrieve word variants: (("improving basic performance series.") OR ("improving based performance based."))*.