Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
van hanh » van thanh, ban hanh, van anh
hanh tai » thanh tai, hang tai, han tai
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
cuc tre » cua tre, cuu tre, cuc thue
duc tre » duoc tren, duc tien
co loi » co hoi

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: tu sach ky nang ((co loi) OR (co hoc)). hieu vien cac duc van hanh tai ((cuc tre) OR (duc tre))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((co loi) or (co hoc)). hieu vien cac duc van hanh tai ((cuc tre) OR (duc tre))~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((co loi) or (co hoc)). hieu vien cac duc van hanh tai ((cuc tre) OR (duc tre))*.