Perhaps you should try some spelling variations:
hien sach » kien sach, thien hach, chieu sach
dien sach » dien anh
trung cua » truong cua, trung tuan, dung cua
trung cap » truong cao, trung tam
dung cong » dung trong
cong dan » cong san, cong tan, huong dan
dan than » dan chan, ban than, van than
than tap » toan tap, han tap, phan tap

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: hoc ((hien sach) OR (dien sach)) - hanh ((trung cua) OR (trung cap)) dung cong dan than tap~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hien sach) OR (dien sach)) - hanh ((trung cua) or (trung cap)) dung cong dan than tap~".
• Adding a wildcard symbol may retrieve word variants: hoc ((hien sach) OR (dien sach)) - hanh ((trung cua) or (trung cap)) dung cong dan than tap*.