Perhaps you should try some spelling variations:
"improving voluntary performance risk." » "improving country performance risk.", "improving entry performance risk.", "improving industry performance risk.", "improving voluntary performance 2019."
"improving firms performance review." » "improving firms performance evidence.", "improving firm performance review.", "improving firm performances review.", "improving funds performance review.", "improving farmers performance review.", "importing firms performance review.", "improving air performance review."

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

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