Perhaps you should try some spelling variations:
dem referat » zum referat
alan david » kaplan david, juan david, bulman david
qian wang » yiqian wang, qian rong, qian yan
liang dem » liang dan, liang wei
jan david » juan david, sahn david, john david
yan wang » yuan wang, yang yang, yan liang
tan » than

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((yan wang) OR (qian wang)) liang dem referat ((jan david) or (alan david)) hong tan ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((yan wang) OR (qian wang)) liang dem referat ((jan david) OR (alan david)) hong tan ;*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((yan wang) OR (qian wang)) liang dem referat ((jan david) or (alan david)) hong tan ;*".