Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hieu xanh » chieu xanh, hieu manh, hieu nganh
trong van » trong cac
doc hieu » toc thieu, hoc thieu, hoc hien
tang van » dang van, hoang van, tang luan
dan than » dan chan, ban than, dan toan
van than » van thanh, van thang, van tuan

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 xanh - hanh ((tang van) or (trong van)) nhung cong ((dan than) OR (van than)) tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu xanh - hanh ((tang van) OR (trong van)) nhung cong ((dan than) OR (van than)) tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu xanh - hanh ((tang van) or (trong van)) nhung cong ((dan than) OR (van than)) tap".
• Adding a wildcard symbol may retrieve word variants: doc hieu xanh - hanh ((tang van) or (trong van)) nhung cong ((dan than) OR (van than)) tap*.