Perhaps you should try some spelling variations:
thanh dai » thanh hai, thanh tai, thanh dat
hieu van » hieu va, thien van, lieu va
cac ban » cac dan, cac van, can ban
dac ban » dac san, duc ban, da ban
van cac » van hac, van cau, van bac
sach ly » sach y, sach lo, sach hay
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, x ho

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