Perhaps you should try some spelling variations:
performance series » performance studies, performance size
performance review » performance risk, performance evidence
poor performance » sector performance
und performance » fund performance, funds performance, good performance
improving poor » improving power, improving food, improving peer
improving und » improving food, improving burn, improving feed

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

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