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 bank performance series." » "improving bank performance metrics.", "improving bank performance reviews.", "improving bank performance targets.", "improving market performance series.", "improving _ performance series.", "improving firm performance series.", "improving land performance series.", "improving urban performance series.", "improving basic 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 bank performance series.") OR ("improving voluntary performance review."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"improving bank performance series.\") OR (\"improving voluntary performance review.\"))".
• Removing quotes may allow a broader search: (( improving bank performance series. ) OR ( improving voluntary performance review. )).
• Adding a wildcard symbol may retrieve word variants: (("improving bank performance series.") OR ("improving voluntary performance review."))*.