Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien dat » vien dai, vien da, viec dat
nuoc van » nuoc va, nuoc san, luoc van
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
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
so hoc » co hoc, mo hoc, so hoa
co loi » co hoi
o hoc » co hoc, mo hoc, y 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 (so hoc))) or (co loi)). hieu vien dat nuoc 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 (so hoc))) OR (co loi)). hieu vien dat nuoc 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 (so hoc))) or (co loi)). hieu vien dat nuoc van hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((((o hoc) OR (so hoc))) or (co loi)). hieu vien dat nuoc van hanh tai cua tre*.