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 series." » "improving building performance series.", "improving specific performance series.", "improving public performance metrics.", "improving public performance reviews.", "improving public performance review.", "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 contract."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving public performance series.") OR ("improving air performance contract."))*.
• Removing quotes may allow a broader search: (( improving public performance series. ) or ( improving air performance contract. ))*.