Perhaps you should try some spelling variations:
"improving ers performance contract." » "improving ers performance contracts.", "improving frs performance contract.", "improving users performance contract.", "improving news performance contract.", "improving erm performance contract.", "improving e performance contract.", "improving eap performance contract."
"improving past performance series." » "improving past performance studies.", "improving past performance size.", "improving plant performance series.", "improving port performance series.", "improving transit performance series.", "improving fast performance series.", "improving post performance series."

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 past performance series.") OR ("improving ers performance contract."))~.
• Removing quotes may allow a broader search: (( improving past performance series. ) or ( improving ers performance contract. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving past performance series.") or ("improving ers performance contract."))*.