Perhaps you should try some spelling variations:
"improving voluntary performance review." » "improving country performance review.", "improving entry performance review.", "improving budgetary performance review.", "improving voluntary performance risk.", "improving voluntary performance evidence."
"improving public performance series." » "improving building performance series.", "improving specific performance series.", "improving public performance metrics.", "improving public performance reviews.", "improving public performance targets.", "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 voluntary performance review."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"improving public performance series.\") OR (\"improving voluntary performance review.\"))".
• Removing quotes may allow a broader search: (( improving public performance series. ) OR ( improving voluntary performance review. )).
• Adding a wildcard symbol may retrieve word variants: (("improving public performance series.") OR ("improving voluntary performance review."))*.