Perhaps you should try some spelling variations:
"improving thermal performance metrics." » "improving thermal performance contracts.", "improving thermal performance measures.", "improving thermal performance contract.", "improving maternal performance metrics.", "improving rural performance metrics.", "improving human performance metrics."
"improving urban performance series." » "improving urban performance reviews.", "improving urban performance review.", "improving urban performance targets.", "improving bank performance series.", "improving loan performance series.", "improving can performance series."

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