Perhaps you should try some spelling variations:
performance contract » performance contracts
performance series » performance studies, performance size
improving export » improving exposure, improving eap, improving eco
top performance » crop performance, do performance, group performance
improving top » improving tfp, improving crop, improving tax

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

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