Perhaps you should try some spelling variations:
"improving thermal performance risk." » "improving maternal performance risk.", "improving rural performance risk.", "improving human performance risk.", "improving thermal performance size.", "improving thermal performance based.", "improving thermal performance _."
"improving food performance evidence." » "improving good performance evidence.", "improving poor performance evidence.", "improving fund performance evidence.", "improving land performance evidence."

You may be able to get more results by adjusting your search query.

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