Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, hieu manh
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
trang va » tran van, hang va
dan than » dan chan, ban than, dan toan
van than » van thanh, van thang, van tuan
lan van » luan van, lang van, tan van

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 nganh - hanh ((trang va) OR (lan van)) dung cong ((dan than) OR (van than)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu nganh - hanh ((trang va) or (lan van)) dung cong ((dan than) OR (van than)) cau~".
• Adding a wildcard symbol may retrieve word variants: doc hieu nganh - hanh ((trang va) or (lan van)) dung cong ((dan than) OR (van than)) cau*.