Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu cua » hieu qua, dieu cua, bieu cua
van hanh » van thanh, ban hanh, van anh
ty mang » ty xang, ty hang, tin mang
mang xa » lang xa, mang may, dang xay
cac tu » cac thu, cach tu, cac du
tu van » tu va
vi cua » vai cua, di cua
cua te » cua tu

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ty mang xa hoi. hieu cua cac tu van hanh vi cua te~".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ty mang xa hoi. hieu cua cac tu van hanh vi cua te*.