Perhaps you should try some spelling variations:
"improving contract performance measures." » "improving country performance measures.", "improving court performance measures.", "improving economic performance measures.", "improve contract performance measures.", "improving central performance measures.", "improve contrast performance measures."
"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."

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 contract performance measures.") or ("improving peer performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving contract performance measures.") OR ("improving peer performance series.")).
• Removing quotes may allow a broader search: (( improving contract performance measures. ) or ( improving peer performance series. )).
• Adding a wildcard symbol may retrieve word variants: (("improving contract performance measures.") or ("improving peer performance series."))*.