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
sach ky » sach y, sach ty, sach kem
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
cuc tre » duc tre, cua tre, cuu tre
sac ky » cac ky, sai ky
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) OR (sac ky)) nang ((co loi) OR (co hoc)). hieu vien cac duc van hanh tai cuc tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sac ky)) nang ((co loi) or (co hoc)). hieu vien cac duc van hanh tai cuc tre~".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) nang ((co loi) or (co hoc)). hieu vien cac duc van hanh tai cuc tre*.