Perhaps you should try some spelling variations:
hieu sach » chieu sach, hieu cach, dien sach
tranh cua » doanh cua, manh cua
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
cua dung » cua dang, cua dong, qua dung
san toan » van toan, manh toan, xuan toan
dan toan » van toan, dan than, manh toan

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 - canh tranh cua dung cong ((san toan) or (dan toan)) cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sach - canh tranh cua dung cong ((san toan) OR (dan toan)) cau.
• Adding a wildcard symbol may retrieve word variants: doc hieu sach - canh tranh cua dung cong ((san toan) or (dan toan)) cau*.