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