Perhaps you should try some spelling variations:
hieu sach » chieu sach, hieu cach, hieu cac
dien sach » dien anh
chua dang » cua dang, chua dong, chua nang
dang cong » dung cong
cong manh » cong danh, duong manh, cong thanh
anh dong » anh huong, anh son
manh van » anh van, menh van, canh van

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 sach) or (dien sach)) - ((canh tranh) or (anh dong)) chua dang cong manh van ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sach) OR (dien sach)) - ((canh tranh) OR (anh dong)) chua dang cong manh van ban.
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sach) or (dien sach)) - ((canh tranh) or (anh dong)) chua dang cong manh van ban*.