Perhaps you should try some spelling variations:
"improving air performance metrics." » "improving air performance measures.", "improving zur performance metrics.", "improving bar performance metrics.", "improving der performance metrics.", "improving _ performance metrics."
"improving music performance evidence." » "improving public performance evidence.", "improving using performance evidence.", "improving seismic performance evidence.", "improving basic performance evidence.", "improvised music performance evidence.", "improving civic performance evidence."

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