Perhaps you should try some spelling variations:
"improving thermal performance series." » "improving thermal performance studies.", "improving thermal performance size.", "improving external performance series.", "improving animal performance series.", "improving erm performance series."
"improving road performance review." » "improving road performance risk.", "improving road performance evidence.", "improving board performance review.", "improving good performance review.", "improving bond performance review.", "improving food performance review.", "improving rural performance review."

Try widening your search to All Fields.

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• Performing a fuzzy search may retrieve terms with similar spellings: (("improving thermal performance series.") or ("improving road performance review."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving thermal performance series.") OR ("improving road performance review.")).
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