Perhaps you should try some spelling variations:
"improving basic performance metrics." » "improving basic performance measures.", "improving based performance metrics.", "improving music performance metrics.", "improving baseline performance metrics.", "improving air performance metrics.", "improve basic performance metrics."
"improving past performance series." » "improving past performance studies.", "improving past performance size.", "improving plant performance series.", "improving port performance series.", "improving transit performance series.", "improving fast performance series.", "improving post performance series."

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving past performance series.") or ("improving basic performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving past performance series.") OR ("improving basic performance metrics.")).
• Removing quotes may allow a broader search: (( improving past performance series. ) or ( improving basic performance metrics. )).
• Adding a wildcard symbol may retrieve word variants: (("improving past performance series.") or ("improving basic performance metrics."))*.