Perhaps you should try some spelling variations:
"improving do performance metrics." » "improving do performance measures.", "improving di performance metrics.", "improving 2 performance metrics.", "improving 3 performance metrics.", "improving co performance metrics.", "improving eco performance metrics.", "improving pro performance metrics."
"improving tax performance series." » "improving tax performance studies.", "improving tax performance size.", "improving box performance series.", "improving cta performance series.", "improving dam performance series.", "improving trade performance series.", "improving data performance series.", "improving care 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 tax performance series.") or ("improving do performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving tax performance series.") OR ("improving do performance metrics.")).
• Removing quotes may allow a broader search: (( improving tax performance series. ) or ( improving do performance metrics. )).
• Adding a wildcard symbol may retrieve word variants: (("improving tax performance series.") or ("improving do performance metrics."))*.