Perhaps you should try some spelling variations:
"improving economic performance series." » "improve economic performance series.", "improved economic performance series.", "improving economic performance studies.", "improving economic performance size."
"improving asset performance risk." » "improving dataset performance risk.", "improving market performance risk.", "improving affect performance risk.", "improving asset performance 2019.", "improving adult performance risk.", "improving audit performance risk.", "improving fast performance risk."

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("improving economic performance series.") or ("improving asset performance risk."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving economic performance series.") OR ("improving asset performance risk.")).
• Removing quotes may allow a broader search: (( improving economic performance series. ) or ( improving asset performance risk. )).
• Adding a wildcard symbol may retrieve word variants: (("improving economic performance series.") or ("improving asset performance risk."))*.