Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, lanh dao
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va cao » va cac, va co, va dao
tuc va » thuc va, truc va, duc va

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 xa) or (nang x)) hoi. hieu va cao ((tuc va) or (tuc xa)) vanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang xa) OR (nang x)) hoi. hieu va cao ((tuc va) OR (tuc xa)) vanh dai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang xa) or (nang x)) hoi. hieu va cao ((tuc va) or (tuc xa)) vanh dai cua tre*.