Perhaps you should try some spelling variations:
"improving firm performance contract." » "improving firm performance contracts.", "improving firms performance contract.", "improving air performance contract.", "improving erm performance contract."
"improving based performance series." » "improving based performance studies.", "improving based performance size.", "improving board performance series.", "improving fund performance series.", "improving good performance series.", "improving basic performance series.", "improving care performance series.", "improving asset 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 firm performance contract.") or ("improving based performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving firm performance contract.") OR ("improving based performance series.")).
• Removing quotes may allow a broader search: (( improving firm performance contract. ) or ( improving based performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving firm performance contract.") or ("improving based performance series."))*.