Perhaps you should try some spelling variations:
hieu dat » bieu dat, hieu dac, hieu luat
dung sai » dung tai, dung va, dung dat
hieu bat » dieu bat, hieu bai, hieu luat
sai cua » dai cua, hai cua, lai cua
va dung » van dung, va duong, vat dung
tu sach » thu sach, su sach, te sach
nang xa » lang xa, nang ma, mang xa
sach ly » sach y, sach lo, sach ty
cua tre » cua te, cuu tre, cua triet

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 ly ((nang xa) or (nang x)) hoi. hien ((hieu dat) OR (hieu bat)) nuoc va dung sai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ly ((nang xa) OR (nang x)) hoi. hien ((hieu dat) OR (hieu bat)) nuoc va dung sai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ly ((nang xa) or (nang x)) hoi. hien ((hieu dat) OR (hieu bat)) nuoc va dung sai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ly ((nang xa) or (nang x)) hoi. hien ((hieu dat) OR (hieu bat)) nuoc va dung sai cua tre*.