Perhaps you should try some spelling variations:
des referates » des referats, den referaten, eines referates
wang wang » wang yang, wang liang, wang yan
von david » john david, jan david
ben david » bevan david
yan wang » yuan wang, yang yang, qian wang
wang des » zwang des, gang des, zwang der
ng tan » hong tan, wing tan

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: yan wang wang des referates ((von david) OR (ben david)) ng tan ;~.
• Adding a wildcard symbol may retrieve word variants: yan wang wang des referates ((von david) or (ben david)) ng tan ;*.