Perhaps you should try some spelling variations:
dong hoang » hong hong
dong yang » wang yang, yang yang, dan yang
dong cao » dong xiao, dan cao, dong nan
a patent » a patient, _ patent, a parent
long du » long d, long do, long run
ya a » a a, y a, ye a
a eu » _ eu, a e, 2 eu
i eu » ii eu, _ eu, i e

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