Perhaps you should try some spelling variations:
hieu sang » chieu sang, hieu lang, hieu quang
nang cong » nang song, dang cong, bang cong
doc hieu » toc thieu, hoc thieu, hoc hien
cong dan » cong san, cong tan, huong dan
dan than » dan chan, ban than, van than
than ban » thanh ban, toan ban, than man
anh anh » thanh anh, hinh anh, minh anh
lan anh » tuan anh
van anh » van thanh, tuan anh, van minh

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: doc hieu sang - ((anh anh) or (((lan anh) or (van anh)))) chuc nang cong dan than ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sang - ((anh anh) OR (((lan anh) OR (van anh)))) chuc nang cong dan than ban.
• Adding a wildcard symbol may retrieve word variants: doc hieu sang - ((anh anh) or (((lan anh) or (van anh)))) chuc nang cong dan than ban*.