Perhaps you should try some spelling variations:
dong yang » dong hoang, wang yang, yang yang
than data » than death, loan data, can data
sang minh » kang minah, anh minh, song min
yang yao » yang yang, wang yan, yang yi
than bad » than bau, than a, than big
how aid » how asia
how ai » how ae, how am, how asia

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 yang yao ((than bad) OR (than data)) sang minh ((how ai) OR (how aid)) ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "dong yang yao ((than bad) or (than data)) sang minh ((how ai) OR (how aid)) ;~".
• Adding a wildcard symbol may retrieve word variants: dong yang yao ((than bad) or (than data)) sang minh ((how ai) OR (how aid)) ;*.