Perhaps you should try some spelling variations:
"image contrast performance metrics." » "image contract performance metrics.", "image contractor performance metrics.", "image control performance metrics.", "image contrast performance measures.", "images contrast performance metrics."
"improving peer performance series." » "improving peer performance studies.", "improving peer performance size.", "improving power performance series.", "improving poor performance series.", "improving der performance series.", "improving gender performance series.", "improving air performance series.", "improving energy 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: (("image contrast performance metrics.") or ("improving peer performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("image contrast performance metrics.") OR ("improving peer performance series."))*.
• Removing quotes may allow a broader search: (( image contrast performance metrics. ) or ( improving peer performance series. ))*.