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 bond performance 2019." » "improving board performance 2019.", "improving fund performance 2019.", "improving good performance 2019.", "improving bond performance _.", "improving bond performance a.", "improving blood performance 2019.", "improving food performance 2019.", "improving beef performance 2019."

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 bond performance 2019."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving thermal performance series.") OR ("improving bond performance 2019.")).
• Removing quotes may allow a broader search: (( improving thermal performance series. ) or ( improving bond performance 2019. )).
• Adding a wildcard symbol may retrieve word variants: (("improving thermal performance series.") or ("improving bond performance 2019."))*.