Perhaps you should try some spelling variations:
"improving human performance contract." » "improving human performance contracts.", "improving loan performance contract.", "improving thermal performance contract.", "improving chain performance contract."
"improving firms performance metrics." » "improving firms performance measures.", "improving firm performance metrics.", "improving firm performances metrics.", "improving funds performance metrics.", "improving farmers performance metrics.", "importing firms performance metrics.", "improving air performance metrics."

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 contract.") or ("improving firms performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving human performance contract.") OR ("improving firms performance metrics."))*.
• Removing quotes may allow a broader search: (( improving human performance contract. ) or ( improving firms performance metrics. ))*.