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

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

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