Perhaps you should try some spelling variations:
yang yang » wang yang, wang yan
dong cao » dong xiao, dong nan, yong cai
a patent » a patient, _ patent, a parent
dan cao » dan cao's
long du » long d, long do, long run
a bau » a bad, a bab, a ban
ya a » a a, y a, ye a
a au » a auf, a aus, a a

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