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
bach tu » bach thu, cach tu, bac tu
tu sach » thu sach, su sach, te sach
nang ro » nang co, nang ho, nang ra
ly nang » ky nang, ly hang, ly vang
cua tre » cua te, cuu tre, cua triet
ro hoi » co hoi, o hoi, mo hoi
dao ve » bao ve, dap ve, dau ve
ve cua » le cua, de cua, te cua
tu ca » tu cac, tu cua, tu can

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 ro hoi. ((hieu tieng) or (thieu nien)) bach tu ca dao ve cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ly nang ro hoi. ((hieu tieng) OR (thieu nien)) bach tu ca dao ve cua tre.
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ly nang ro hoi. ((hieu tieng) or (thieu nien)) bach tu ca dao ve cua tre*.