Perhaps you should try some spelling variations:
"improving crop performance metrics." » "improving crop performance measures.", "improving group performance metrics.", "improving top performance metrics.", "improving do performance metrics.", "improving co performance metrics.", "improving pro performance metrics.", "improving macro 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."

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

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