Perhaps you should try some spelling variations:
"improving loan performance series." » "improving loan performance studies.", "improving loan performance size.", "improving local performance series.", "improving land performance series.", "improving lead performance series."
"improving mental performance series." » "improving mental performance studies.", "improving mental performance size.", "improving general performance series.", "improving senegal performance series.", "improving annual performance series.", "improving maternal performance series.", "improving fiscal performance series.", "improving gender 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 loan performance series.") or ("improving mental performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving loan performance series.") OR ("improving mental performance series.")).
• Removing quotes may allow a broader search: (( improving loan performance series. ) or ( improving mental performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving loan performance series.") or ("improving mental performance series."))*.