Perhaps you should try some spelling variations:
"improving thermal performance contracts." » "improving external performance contracts.", "improving animal performance contracts.", "improving erm performance contracts."
"improving firms performance evidence." » "improving firm performance evidence.", "improving firm performances evidence.", "improving funds performance evidence.", "improving farmers performance evidence.", "importing firms performance evidence.", "improving air 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 thermal performance contracts.") OR ("improving firms performance evidence."))~.
• Removing quotes may allow a broader search: (( improving thermal performance contracts. ) or ( improving firms performance evidence. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving thermal performance contracts.") or ("improving firms performance evidence."))*.