Perhaps you should try some spelling variations:
"improving present performance metrics." » "improving recent performance metrics.", "improving precedent performance metrics.", "improving project performance metrics.", "improving present performance measures.", "improving patient performance metrics.", "improving payment performance metrics."
"improving human performance series." » "improving human performance studies.", "improving human performance size.", "improving loan performance series.", "improving thermal performance series.", "improving chain 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 human performance series.") or ("improving present performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving human performance series.") OR ("improving present performance metrics.")).
• Removing quotes may allow a broader search: (( improving human performance series. ) or ( improving present performance metrics. )).
• Adding a wildcard symbol may retrieve word variants: (("improving human performance series.") or ("improving present performance metrics."))*.