Perhaps you should try some spelling variations:
"improving human performance contract." » "improving human performance contracts.", "improving loan performance contract.", "improving thermal performance contract.", "improving chain performance contract."
"improving firm performances review." » "improving firm performance review.", "improving firm performance reviews.", "improving firm performances series.", "improving firms performance review.", "improving from performance review.", "improving firms performances review.", "improving air performances review.", "improving erm performances review."

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 human performance contract.") or ("improving firm performances review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving human performance contract.") OR ("improving firm performances review.")).
• Removing quotes may allow a broader search: (( improving human performance contract. ) or ( improving firm performances review. )).
• Adding a wildcard symbol may retrieve word variants: (("improving human performance contract.") or ("improving firm performances review."))*.