Perhaps you should try some spelling variations:
"improving thermal performance issues." » "improving thermal performance based.", "improving thermal performance size.", "improving thermal performance index.", "improving maternal performance issues.", "improving rural performance issues.", "improving human performance issues."
"improving urban performance measures." » "improving bank performance measures.", "improving loan performance measures.", "improving can performance measures."

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

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