Perhaps you should try some spelling variations:
"improving transit performance evidence." » "improving transport performance evidence.", "improving trade performance evidence.", "improving plant performance evidence.", "improving paratransit performance evidence.", "improving transitions performance evidence."
"improving basic performance series." » "improving basic performance studies.", "improving basic performance size.", "improving based performance series.", "improving music performance series.", "improving baseline performance series.", "improving air performance series.", "improve basic 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 basic performance series.") or ("improving transit performance evidence."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving basic performance series.") OR ("improving transit performance evidence.")).
• Removing quotes may allow a broader search: (( improving basic performance series. ) or ( improving transit performance evidence. )).
• Adding a wildcard symbol may retrieve word variants: (("improving basic performance series.") or ("improving transit performance evidence."))*.