Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
ban hanh » ban hang
nuoc ban » nuoc san, quoc ban, buoc ban
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
tu sach » thu sach, su sach, tu cach
hieu va » lieu va, hieu qua
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
te sach » toc sach
nang o » nang co, nang ho, nang ro
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: ((tu sach) OR (te sach)) ky nang o hai. ((hieu ve) or (hieu va)) cac nuoc ban hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) ky nang o hai. ((hieu ve) OR (hieu va)) cac nuoc ban hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (te sach)) ky nang o hai. ((hieu ve) or (hieu va)) cac nuoc ban hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (te sach)) ky nang o hai. ((hieu ve) or (hieu va)) cac nuoc ban hanh tai cua tre*.