Perhaps you should try some spelling variations:
berlin reform » berlin referat
liang berlin » lang berlin, lange berlin, leidig berlin
yang liang » wang liang, yan liang, yang yang
reform 3.1 » reform 4.1, reform 5.3.1, reform 1
david dang » david ian, david mant, david ng
wang yang » wang yan, wang liang, wang yanling

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: wang yang liang berlin reform 3.1 ((david dang) OR (david a)) hai ;~.
• Adding a wildcard symbol may retrieve word variants: wang yang liang berlin reform 3.1 ((david dang) or (david a)) hai ;*.