Perhaps you should try some spelling variations:
toc sac » toc sach, toc san, hoc sach
viet ca » viet ha, viet co, viet a
va hanh » van hanh, va thanh, ban hanh
va danh » va dinh, va dan, dia danh
hieu ve » hieu va, hieu van
mang xa » lang xa, mang may, dang xay
tang ma » mang may, tang van
ca theo » cau theo, va theo, chan theo
sac ky » cac ky, sai ky
ve cau » ke cau, va cau, ve cac

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: toc sac ky ((mang xa) OR (tang ma)) hoi. hieu ve cau tao ((va danh) OR (va hanh)) viet ca theo~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sac ky ((mang xa) or (tang ma)) hoi. hieu ve cau tao ((va danh) OR (va hanh)) viet ca theo~".
• Adding a wildcard symbol may retrieve word variants: toc sac ky ((mang xa) or (tang ma)) hoi. hieu ve cau tao ((va danh) OR (va hanh)) viet ca theo*.