Perhaps you should try some spelling variations:
research experiments » research experimental, research experience, research experiences
handel research » channel research, panel research, handover research
hanse research » change research, kansei research, sansei research
online ratings » online dating, online trainings, online meetings
online rating » online dating, online creating, online routing
online ring » online during, online racing, online string

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) OR (hanse research)) documents ) OR ( ((online ratings) OR (((online ring) OR (online rating)))) research experiments )).
• Adding a wildcard symbol may retrieve word variants: (( online ((handel research) or (hanse research)) documents ) or ( ((online ratings) or (((online ring) or (online rating)))) research experiments ))*.