Perhaps you should try some spelling variations:
"improving poor performance contract." » "improving poor performance contracts.", "improving sector performance contract.", "improving power performance contract.", "improving food performance contract.", "improving peer performance contract."
"improving thermal performance series." » "improving thermal performance studies.", "improving thermal performance size.", "improving external performance series.", "improving animal performance series.", "improving erm 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 thermal performance series.") OR ("improving poor performance contract."))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"improving thermal performance series.\") OR (\"improving poor performance contract.\"))".
• Removing quotes may allow a broader search: (( improving thermal performance series. ) OR ( improving poor performance contract. )).
• Adding a wildcard symbol may retrieve word variants: (("improving thermal performance series.") OR ("improving poor performance contract."))*.