Perhaps you should try some spelling variations:
hieu lang » chieu sang, hieu quang, nhieu tang
trong xay » trong cac, trong ca, trong san
trong tan » trong quan, trong cac, trong ca
tan thanh » tran thanh, tang thanh, toan thanh
thanh cac » hanh cac, thanh bac, thanh ca
doc hieu » toc thieu, hoc thieu, hoc hien

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: doc hieu lang - thanh ((trong xay) OR (thong xay)) dung trong tan thanh cac~.
• Adding a wildcard symbol may retrieve word variants: doc hieu lang - thanh ((trong xay) or (thong xay)) dung trong tan thanh cac*.