Perhaps you should try some spelling variations:
"improving urban performance contract." » "improving urban performance contracts.", "improving bank performance contract.", "improving loan performance contract.", "improving human performance contract."
"improving basic performance series." » "improving basic performance studies.", "improving basic performance size.", "improving based performance series.", "improving music performance series.", "improving baseline performance series.", "improving air performance series.", "improve basic 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 basic performance series.") or ("improving urban performance contract."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving basic performance series.") OR ("improving urban performance contract.")).
• Removing quotes may allow a broader search: (( improving basic performance series. ) or ( improving urban performance contract. )).
• Adding a wildcard symbol may retrieve word variants: (("improving basic performance series.") or ("improving urban performance contract."))*.