Perhaps you should try some spelling variations:
hieu tach » hieu cach, chiet tach, chieu sach
tang luan » dung luan
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
mang cua » manh cua, dung cua, ban cua
cong san » cong tac
san toan » van toan, dan toan, manh toan
toan ban » van ban

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 tach - hanh ((((nang cao) or (mang cua))) or (tang luan)) dung cong san toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu tach - hanh ((((nang cao) OR (mang cua))) OR (tang luan)) dung cong san toan ban.
• Adding a wildcard symbol may retrieve word variants: doc hieu tach - hanh ((((nang cao) or (mang cua))) or (tang luan)) dung cong san toan ban*.