Perhaps you should try some spelling variations:
"production frontiers section" » "production functions section", "production factors section", "production frontier section"
"production frontier functions" » "production wannier functions", "production frontier section"
"production frontier region" » "production frontal region"

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: (((("production frontiers section") OR ("production frontier functions"))) OR ("production frontier region")).
• Removing quotes may allow a broader search: (((( production frontiers section ) or ( production frontier functions ))) or ( production frontier region )).
• Adding a wildcard symbol may retrieve word variants: (((("production frontiers section") or ("production frontier functions"))) or ("production frontier region"))*.