Perhaps you should try some spelling variations:
hieu tieng » viet tieng, dien tieng, tiep tieng
thieu nien » thien nhien
toc sach » hoc sach, doc sach, thuoc sach
vai cua » dai cua, hai cua, lai cua
dao vai » dao van, dao va, dao bai
cac dao » cac dan, ca dao, cac dai
bach tu » bach thu, cach tu, bac tu
tu sach » thu sach, su sach, te sach
ly nang » ky nang, ly hang, ly vang
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) or (toc sach)) ly nang o hoi. ((hieu tieng) or (thieu nien)) bach tu cac dao vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ly nang o hoi. ((hieu tieng) OR (thieu nien)) bach tu cac dao vai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ly nang o hoi. ((hieu tieng) or (thieu nien)) bach tu cac dao vai cua tre*.