Perhaps you should try some spelling variations:
"improve contract performance metrics." » "improve country performance metrics.", "improve court performance metrics.", "improve corporate performance metrics.", "improve contract performance contracts.", "improve contract performance measures.", "improve contract performance contract."
"improving air performance series." » "improving air performance reviews.", "improving air performance review.", "improving air performance targets.", "improving firm performance series.", "improving a performance series.", "improving ii performance series.", "improving water performance series.", "improving land performance series.", "improving _ 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: (("improve contract performance metrics.") or ("improving air performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improve contract performance metrics.") OR ("improving air performance series.")).
• Removing quotes may allow a broader search: (( improve contract performance metrics. ) or ( improving air performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improve contract performance metrics.") or ("improving air performance series."))*.