Perhaps you should try some spelling variations:
research documents » search document, research arguments, research comments
research elements » research experiments, research effects, research students
handel research » channel research, panel research, hanse research
online dating » online data, online marketing
online during » online sharing
online rating » online ratings, online creating, online routing

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: (( online handel research documents ) OR ( ((online dating) OR (((online during) OR (online rating)))) research elements )).
• Adding a wildcard symbol may retrieve word variants: (( online handel research documents ) or ( ((online dating) or (((online during) or (online rating)))) research elements ))*.