Perhaps you should try some spelling variations:
vien cac » vien bach, vien dai, gian cac
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
vien da » vien dai, hien dai
tai cua » thai cua, tai cuc, tri cua
luc van » luoc van, luu van, duc van
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
co loi » co hoi
o hoc » co hoc, mo hoc, so hoc

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 ((o hoc) or (co loi)). hieu ((vien cac) OR (vien da)) luc van hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoc) OR (co loi)). hieu ((vien cac) OR (vien da)) luc van hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoc) or (co loi)). hieu ((vien cac) OR (vien da)) luc van hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoc) or (co loi)). hieu ((vien cac) OR (vien da)) luc van hanh tai cua tre*.