Perhaps you should try some spelling variations:
"improving seismic performance series." » "improving economic performance series.", "improving academic performance series.", "improving seismic performance studies.", "improving seismic performance size.", "improving semantic performance series.", "improving service performance series.", "improving basic performance series."
"improving port performance risk." » "improving export performance risk.", "improving court performance risk.", "improving plant performance risk.", "improving port performance 2019.", "improving post performance risk.", "improving poor performance risk."

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

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