Perhaps you should try some spelling variations:
"improving air performance review." » "improving air performance evidence.", "improving a performance review.", "improving ii performance review.", "improving miv performance review.", "improving water performance review.", "improving land performance review.", "improving _ performance review."
"improving firm performance risk." » "improving _ performance risk.", "improving firm performance size.", "improving firm performance based.", "improving firm performance _.", "improving firms performance risk.", "improving birth performance risk.", "improving food performance risk."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving firm performance risk.") or ("improving air performance review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving firm performance risk.") OR ("improving air performance review.")).
• Removing quotes may allow a broader search: (( improving firm performance risk. ) or ( improving air performance review. )).
• Adding a wildcard symbol may retrieve word variants: (("improving firm performance risk.") or ("improving air performance review."))*.