Perhaps you should try some spelling variations:
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
cai hoi » dai hoi, cai hoa, lai hoi
hieu ke » hieu kem, chieu ke, hieu ky
va hanh » van hanh, va thanh, va danh
lai cua » dai cua, lai chau, thai cua
hai cua » thai cua, dai cua, hoi cua
ke cau » ket cau
cau tu » dau tu, cau truc

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang ((cai hoi) or (cau hoi)). hieu ke cau tu va hanh ((lai cua) OR (hai cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang ((cai hoi) OR (cau hoi)). hieu ke cau tu va hanh ((lai cua) OR (hai cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang ((cai hoi) or (cau hoi)). hieu ke cau tu va hanh ((lai cua) OR (hai cua)) te".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang ((cai hoi) or (cau hoi)). hieu ke cau tu va hanh ((lai cua) OR (hai cua)) te*.