Perhaps you should try some spelling variations:
"improve materials performance evidence." » "improve managerial performance evidence.", "improve metrics performance evidence.", "improve ministerial performance evidence.", "improve maternal performance evidence.", "improved material performance evidence.", "improve matern performance evidence."
"improving human performance contract." » "improving human performance contracts.", "improving loan performance contract.", "improving thermal performance contract.", "improving chain performance contract."

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