Perhaps you should try some spelling variations:
referaten von » referat von, referat vom, reformen von
reform von » form von
david hong » david ng
chen wang » chen yang, chen rong, chen ping
wen wang » wei wang, weng fang, men want
wang wei » zhang wei, wang zhi
tan » than

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: ((wen wang) OR (chen wang)) wang wei ((referaten von) OR (reform von)) david hong tan ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((wen wang) OR (chen wang)) wang wei ((referaten von) or (reform von)) david hong tan ;~".
• Adding a wildcard symbol may retrieve word variants: ((wen wang) OR (chen wang)) wang wei ((referaten von) or (reform von)) david hong tan ;*.