Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
thi cua » thai cua, thi cuc, tri cua
dan thi » dang thi, tran thi, dinh thi
cac tac » cac toc, cac bac, cac dac
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang xa » lang xa, nang ma, mang xa
va dan » ca dan, va dao, va dau
cac tu » cac thu, cach tu, cac du

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