Perhaps you should try some spelling variations:
"improving human performance contract." » "improving human performance contracts.", "improving loan performance contract.", "improving company performance contract.", "improving animal performance contract.", "improving urban performance contract.", "improving rural performance contract."
"improving thermal performance evidence." » "improving maternal performance evidence.", "improving rural performance evidence.", "improving mental performance evidence."

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