Perhaps you should try some spelling variations:
"improving urban performance series." » "improving urban performance studies.", "improving urban performance size.", "improving bank performance series.", "improving loan performance series.", "improving human performance series."
"improving animal performance series." » "improving animal performance studies.", "improving animal performance size.", "improving annual performance series.", "improving thermal performance series.", "improving fiscal performance series.", "improving initial performance series.", "improving optimal performance series.", "improving criminal 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 animal performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving urban performance series.") OR ("improving animal performance series.")).
• Removing quotes may allow a broader search: (( improving urban performance series. ) or ( improving animal performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving urban performance series.") or ("improving animal performance series."))*.