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