Perhaps you should try some spelling variations:
"improving country performance review." » "improving country performance risk.", "improving country performance evidence.", "improving voluntary performance review.", "importing country performance review.", "improving community performance review."
"improving power performance series." » "improving power performance studies.", "improving power performance size.", "improving poor performance series.", "improving worker performance series.", "improving core performance series.", "improving peer performance series.", "improving sewer 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 country performance review.") or ("improving power performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving country performance review.") OR ("improving power performance series.")).
• Removing quotes may allow a broader search: (( improving country performance review. ) or ( improving power performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving country performance review.") or ("improving power performance series."))*.