Perhaps you should try some spelling variations:
commercial crops » commercial code, commercial credit, commercial banks
brief selective » driven selective, area selective, based selective
based relative » based reflective, based receptive, based selective
case relative » das relative, male relative, same relative
sage studies » scale studies, state studies, case studies

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

• Performing a fuzzy search may retrieve terms with similar spellings: commercial crops _ ((((based relative) or (brief selective))) or (case relative)) sage studies.~.
• If you are trying to use Boolean operators, they must be ALL CAPS: commercial crops _ ((((based relative) OR (brief selective))) OR (case relative)) sage studies..
• Adding a wildcard symbol may retrieve word variants: commercial crops _ ((((based relative) or (brief selective))) or (case relative)) sage studies.*.