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