Perhaps you should try some spelling variations:
"improving air performance metrics." » "improving air performance contracts.", "improving air performance measures.", "improving air performance contract.", "improving firm performance metrics.", "improving a performance metrics.", "improving ii performance metrics.", "improving water performance metrics.", "improving land performance metrics.", "improving _ performance metrics."
"improving public performance series." » "improving building performance series.", "improving specific performance series.", "improving public performance reviews.", "improving public performance review.", "improving public performance targets.", "improving quality performance series."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving public performance series.") or ("improving air performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving public performance series.") OR ("improving air performance metrics."))*.
• Removing quotes may allow a broader search: (( improving public performance series. ) or ( improving air performance metrics. ))*.