Perhaps you should try some spelling variations:
"improving poor performance metrics." » "improving poor performance measures.", "improving sector performance metrics.", "improving power performance metrics.", "improving food performance metrics.", "improving peer 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 poor performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving tax performance series.") OR ("improving poor performance metrics.")).
• Removing quotes may allow a broader search: (( improving tax performance series. ) or ( improving poor performance metrics. )).
• Adding a wildcard symbol may retrieve word variants: (("improving tax performance series.") or ("improving poor performance metrics."))*.