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