Perhaps you should try some spelling variations:
den referaten » dem referat, den reformen, des referats
des referates » des referats, eines referates, des referenten
wang liang » wang yang
von david » john david, jan david
ben david » bevan david
wan wang » wen wang, yan wang, wang yang
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: wan wang liang ((des referates) OR (den referaten)) ((von david) OR (ben david)) ng tan ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "wan wang liang ((des referates) OR (den referaten)) ((von david) or (ben david)) ng tan ;~".
• Adding a wildcard symbol may retrieve word variants: wan wang liang ((des referates) OR (den referaten)) ((von david) or (ben david)) ng tan ;*.