Perhaps you should try some spelling variations:
hieu sach » chieu sach, hieu cach, dien sach
doc hieu » toc thieu, hoc thieu, hoc hien
cdinh cu » chinh cau, chinh cua, dinh cuu
toan tap » toan ban
dinh cu » dinh cuu, dinh chuc, dinh chau
con dan » cong dan, co dan, con day
con ban » con bang, co ban, can ban

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 sach - hanh ((cdinh cu) OR (dinh cu)) thuong ((con dan) OR (con ban)) toan tap~.
• Adding a wildcard symbol may retrieve word variants: doc hieu sach - hanh ((cdinh cu) or (dinh cu)) thuong ((con dan) or (con ban)) toan tap*.