Perhaps you should try some spelling variations:
thieu sach » chieu sach, thien hach, theo sach
thanh tinh » thanh binh, nhanh tinh, than kinh
hieu cach » hieu cac, chieu sach, hieu ca
hang cong » dang cong, hang nong, bang cong
tinh cua » trinh cua, sinh cua, tinh chat
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan 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 ((thieu sach) OR (hieu cach)) - thanh tinh cua ((hang cong) OR (han tong)) dan toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thieu sach) OR (hieu cach)) - thanh tinh cua ((hang cong) or (han tong)) dan toan cau~".
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu sach) OR (hieu cach)) - thanh tinh cua ((hang cong) or (han tong)) dan toan cau*.