Perhaps you should try some spelling variations:
"improving past performance based." » "improving past performance measures.", "improving plant performance based.", "improving port performance based.", "improving based performance based.", "improving basic performance based.", "improving asset performance based.", "improving land performance based."
"improving air performance risk." » "improving air performance size.", "improving air performance _.", "improving air performance data.", "improving firm performance risk.", "improving a performance risk.", "improving ii performance risk.", "improving water performance risk.", "improving land performance risk.", "improving _ performance risk."

Try widening your search to All Fields.

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

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