Perhaps you should try some spelling variations:
cac nuoc » cap nuoc, dat nuoc, cua nuoc
hanh lai » hanh lam, hanh tai, thanh lap
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » hieu qua
va hanh » van hanh, va thanh, va danh
lai cua » dai cua, hai cua, lai chau
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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