Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
van hanh » van thanh, ban hanh, van anh
sach ky » sac ky, sach y, sach ty
va hanh » va thanh, va danh, ban hanh
cac tac » cac toc, cac bac, cac dac
cu tren » tu tren, dua tren
hieu ve » hieu va, hieu van
co hoi » co hoc
ve cac » va cac, vien cac
ve cu » ve cau, ve chu, ve cua

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: thuat sach ky nang ((co hoi) OR (co loi)). hieu ve cac tac ((va hanh) OR (van hanh)) ve cu tren~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach ky nang ((co hoi) or (co loi)). hieu ve cac tac ((va hanh) OR (van hanh)) ve cu tren~".
• Adding a wildcard symbol may retrieve word variants: thuat sach ky nang ((co hoi) or (co loi)). hieu ve cac tac ((va hanh) OR (van hanh)) ve cu tren*.