Perhaps you should try some spelling variations:
thanh trung » thanh tung
hieu sach » chieu sach, hieu cach, hieu cac
dien sach » dien anh
dung cong » dung trong
trung va » truong va, trang va, trung ha
cong tac » cong ty
bang cau » hang cau, bang cac, nang cao
va dung » van dung, va duong, vat dung
ran cau » van cau, ban cau, can cau

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) OR (dien sach)) - thanh trung va dung cong tac ((ran cau) OR (bang cau))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sach) OR (dien sach)) - thanh trung va dung cong tac ((ran cau) or (bang cau))~".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sach) OR (dien sach)) - thanh trung va dung cong tac ((ran cau) or (bang cau))*.