Perhaps you should try some spelling variations:
"improving overall performance contract." » "improving overall performance contracts.", "improving average performance contract.", "improving thermal performance contract.", "improving governance performance contract.", "improving coverage performance contract.", "improving rural performance contract.", "improving federal performance contract."
"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."

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