Perhaps you should try some spelling variations:
"improving logistics performance contracts." » "improving cognitive performance contracts."
"improving air performance based." » "improving air performance measures.", "improving firm performance based.", "improving a performance based.", "improving ii performance based.", "improving water performance based.", "improving land performance based.", "improving _ performance based."

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

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