Perhaps you should try some spelling variations:
"improving air performance based." » "improving air performance measures.", "improving firm performance based.", "improving a performance based.", "improving ii performance based.", "improving water performance based.", "improving land performance based.", "improving _ performance based."
"improving thermal performance risk." » "improving maternal performance risk.", "improving rural performance risk.", "improving human performance risk.", "improving thermal performance size.", "improving thermal performance _.", "improving thermal performance data."

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

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