Perhaps you should try some spelling variations:
"improving country performance series." » "improving country performance metrics.", "improving country performance reviews.", "improving country performance review.", "improving voluntary performance series.", "importing country performance series.", "borrowing country performance series."
"improving sector performance series." » "improving sector performance metrics.", "improving sector performance reviews.", "improving sector performance review.", "improving export performance series.", "improve sector performance series.", "improving teacher performance series.", "improving weather performance series."

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