Perhaps you should try some spelling variations:
"improve national performance series." » "improve regional performance series.", "improve operational performance series.", "improve educational performance series.", "improve national performance studies.", "improve national performance size.", "improve relational performance series.", "improve maternal performance series.", "improvement national performance series."
"improving maternal performance reports." » "improving materials performance reports.", "improving external performance reports.", "improving managerial performance reports.", "improve maternal performance reports.", "improving water performance reports.", "improving maternal performance report."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("improve national performance series.") or ("improving maternal performance reports."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improve national performance series.") OR ("improving maternal performance reports.")).
• Removing quotes may allow a broader search: (( improve national performance series. ) or ( improving maternal performance reports. )).
• Adding a wildcard symbol may retrieve word variants: (("improve national performance series.") or ("improving maternal performance reports."))*.