Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
nuoc van » nuoc va, nuoc san, luoc van
cap nuoc » dat nuoc
sach ky » sac ky, sach y, sach ty
van cap » van cau, van dap, van ca
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc
va cua » va chua, via cua, ca cua
o hai » co hai, so hai, o lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky nang ((((co hoi) or (co loi))) or (o hai)). hieu van cap nuoc van hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ((((co hoi) OR (co loi))) OR (o hai)). hieu van cap nuoc van hanh va cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ((((co hoi) or (co loi))) or (o hai)). hieu van cap nuoc van hanh va cua tre*.