Perhaps you should try some spelling variations:
wei referaten » den referaten, des referates
yuan wang » yan wang, yuan chang, qian wang
yuan kang » yuan chang, chan kang, yuan kai
von david » john david, jan david
ben david » bevan david
wang wei » zhang wei, wang zhi
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: ((yuan wang) OR (yuan kang)) wang wei referaten ((von david) OR (ben david)) ng tan ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((yuan wang) OR (yuan kang)) wang wei referaten ((von david) or (ben david)) ng tan ;~".
• Adding a wildcard symbol may retrieve word variants: ((yuan wang) OR (yuan kang)) wang wei referaten ((von david) or (ben david)) ng tan ;*.