Perhaps you should try some spelling variations:
nhung tuong » nhung huong, nhung phuong, hung vuong
hieu lang » chieu sang, hieu quang, nhieu tang
tang luan » dung luan
van thanh » ban thanh, van tuan
hoc hieu » hoc thieu, hoc hien, doc hieu
tang cua » mang cua, hang cua, thong cua
van toan » van tuan, van tan, manh toan

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: hoc hieu lang - hanh ((tang cua) OR (tang luan)) nhung tuong ((van toan) OR (van thanh)) cau~.
• Adding a wildcard symbol may retrieve word variants: hoc hieu lang - hanh ((tang cua) or (tang luan)) nhung tuong ((van toan) or (van thanh)) cau*.