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 luc » cau luc, coc luc, cac nuoc
luc van » luoc van, luu van, duc van
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
mo hoc » mon hoc, co hoc
co loi » co hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang ((mo hoc) or (co loi)). hieu vien cac luc van hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((mo hoc) OR (co loi)). hieu vien cac luc van hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((mo hoc) or (co loi)). hieu vien cac luc van hanh tai cua tre*.