Perhaps you should try some spelling variations:
"improving brain performance studies." » "improving brain performance audits.", "improving brain performance audit.", "improving brain performance standards.", "improving chain performance studies.", "improving loan performance studies.", "improving can performance studies.", "improving rail performance studies.", "improving air performance studies.", "improving basic performance studies."
"improving job performance series." » "improving job performance size.", "improving court performance series.", "improving co performance series.", "improving food performance series.", "improving crop performance series."

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

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