Perhaps you should try some spelling variations:
"improving co performance series." » "improving co performance metrics.", "improving co performance reviews.", "improving co performance review.", "improving do performance series.", "improving crop performance series.", "improving job performance series.", "improving _ performance series.", "improving macro performance series.", "improving food performance series."
"improving urban performance risks." » "improving bank performance risks.", "improving loan performance risks.", "improving can performance risks.", "improving urban performance risk.", "improving urban performance issues.", "improving urban performance based."

Try widening your search to All Fields.

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