Perhaps you should try some spelling variations:
thieu nien » thien nhien
va triet » va thiet, va trien, ve triet
thanh di » thanh doi, thanh de, thanh do
nuoc ban » nuoc san, quoc ban, buoc ban
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
nien cac » vien cac, dien cac, bien cac
hoc sach » hoc sinh, hoc cac, hoc anh
hanh de » hanh ve, hanh kem
te sach » toc sach
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: ((te sach) or (hoc sach)) ky nang o hoi. thieu nien cac nuoc ban ((thanh di) or (hanh de)) va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (hoc sach)) ky nang o hoi. thieu nien cac nuoc ban ((thanh di) OR (hanh de)) va triet.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (hoc sach)) ky nang o hoi. thieu nien cac nuoc ban ((thanh di) or (hanh de)) va triet*.