Perhaps you should try some spelling variations:
"improving brain performance metrics." » "improving brain performance measures.", "improving chain performance metrics.", "improving loan performance metrics.", "improving can performance metrics.", "improving rail performance metrics.", "improving air performance metrics.", "improving basic performance metrics."
"improving overall performance contracts." » "improving average performance contracts.", "improving thermal performance contracts.", "improving governance performance contracts.", "improving coverage performance contracts.", "improving rural performance contracts.", "improving federal performance contracts."

Try widening your search to All Fields.

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