Perhaps you should try some spelling variations:
yang yang » wang yang, wang yan
dong cao » dong xiao, dan cao, dong nan
patent a » patient a, patents a, patent _
au long » a long, eu long, lam long
long du » long d, long do, long run
ya a » a a, ye a, yu a
a au » a auf, a bau, a aus
y a » y la

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: ((dong cao) OR (yang yang)) ((ya a) OR (y a)) patent a au long du ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((dong cao) or (yang yang)) ((ya a) OR (y a)) patent a au long du ;~".
• Adding a wildcard symbol may retrieve word variants: ((dong cao) or (yang yang)) ((ya a) OR (y a)) patent a au long du ;*.