Perhaps you should try some spelling variations:
"improving human performance contract." » "improving human performance contracts.", "improving loan performance contract.", "improving thermal performance contract.", "improving company performance contract.", "improving urban performance contract.", "improving rural performance contract."
"improving farmers performance series." » "improving firms performance series.", "improving markets performance series.", "improving workers performance series.", "improving farmers performance metrics.", "improving farmers performance reviews.", "improving farmers performance review.", "improving access performance series.", "improving water performance series.", "improving market 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: (("improving human performance contract.") or ("improving farmers performance series."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving human performance contract.") OR ("improving farmers performance series."))*.
• Removing quotes may allow a broader search: (( improving human performance contract. ) or ( improving farmers performance series. ))*.