Perhaps you should try some spelling variations:
trinh thi » trinh tai, dinh thi, trinh tu
tang van » dang van, hoang van, trong van
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
thi cua » thai cua, thi cuc, tri cua
qua cac » cua cac
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa
luc va » duc va, loc 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 ty ((tang van) or (lang xa)) hoi. hieu qua cac ((tuc va) or (luc va)) trinh thi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((tang van) OR (lang xa)) hoi. hieu qua cac ((tuc va) OR (luc va)) trinh thi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((tang van) or (lang xa)) hoi. hieu qua cac ((tuc va) or (luc va)) trinh thi cua tre*.