Perhaps you should try some spelling variations:
performance contract » performance contracts
performance series » performance studies, performance size
burn performance » turn performance, run performance, human performance
improving burn » improving birth, improving human, improving brain
improving bank » improving urban, improving basic, improving brain

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

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