Perhaps you should try some spelling variations:
"improving firms performance reviews." » "improving firms performance review.", "improving firms performance reports.", "improving firms performance risks.", "improving firm performance reviews.", "improving firm performances reviews.", "improving funds performance reviews.", "improving farmers performance reviews.", "improving air performance reviews.", "improving birth performance reviews."
"improving human performance measures." » "improving loan performance measures.", "improving thermal performance measures.", "improving company performance measures.", "improving urban performance measures.", "improving rural performance measures."

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