Perhaps you should try some spelling variations:
thanh gia » thanh gian, thanh giang, thanh nghia
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach ty, sach kem
van cac » van hac, van cau, van bac
gia cua » gian cua, giau cua, gia cuc
cua tre » cua te, cuu tre, cua triet
lo van » le van, so van, do van
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: thuoc ((sach ky) OR (sach y)) nang x hoi. hieu van cac ((lo van) or (vo van)) thanh gia cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuoc ((sach ky) OR (sach y)) nang x hoi. hieu van cac ((lo van) OR (vo van)) thanh gia cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuoc ((sach ky) OR (sach y)) nang x hoi. hieu van cac ((lo van) or (vo van)) thanh gia cua tre".
• Adding a wildcard symbol may retrieve word variants: thuoc ((sach ky) OR (sach y)) nang x hoi. hieu van cac ((lo van) or (vo van)) thanh gia cua tre*.