Perhaps you should try some spelling variations:
"improving human performance series." » "improving human performance studies.", "improving human performance size.", "improving loan performance series.", "improving thermal performance series.", "improving chain performance series."
"improving indoor performance risk." » "improving outdoor performance risk.", "improving poor performance risk.", "improving donor performance risk.", "improving india's performance risk.", "improving food performance risk.", "improving gender performance risk.", "improving indoor performance 2019."

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

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