Perhaps you should try some spelling variations:
"improving thermal performance contract." » "improving thermal performance contracts.", "improving external performance contract.", "improving animal performance contract.", "improving erm performance contract."
"improve maternal performance review." » "improve materials performance review.", "improve external performance review.", "improve national performance review.", "improve maternal performance risk.", "improve maternal performance evidence.", "improving maternal performance review.", "improve water performance review."

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving thermal performance contract.") or ("improve maternal performance review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving thermal performance contract.") OR ("improve maternal performance review."))*.
• Removing quotes may allow a broader search: (( improving thermal performance contract. ) or ( improve maternal performance review. ))*.