Perhaps you should try some spelling variations:
"improving teacher performance contract." » "improving teacher performance contracts.", "improving sector performance contract.", "improving teaching performance contract.", "improving gender performance contract.", "improving trade performance contract."
"improving urban performance series." » "improving urban performance studies.", "improving urban performance size.", "improving bank performance series.", "improving loan performance series.", "improving human performance series."

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

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