Perhaps you should try some spelling variations:
thien van » thi van
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, lieu va, hieu ve
cham duc » pham duc, cham soc, pham duy
hanh dai » hanh tai, hanh dao, vanh dai
sach ty » sach y, sach tu, xach tay
xang xa » lang xa, mang xa, ang xa
va hanh » van hanh, va thanh, va danh
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: doc ((sach ty) OR (sach thu)) xang xa hoi. ((hieu van) or (thien van)) cham duc va hanh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((sach ty) OR (sach thu)) xang xa hoi. ((hieu van) OR (thien van)) cham duc va hanh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((sach ty) OR (sach thu)) xang xa hoi. ((hieu van) or (thien van)) cham duc va hanh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: doc ((sach ty) OR (sach thu)) xang xa hoi. ((hieu van) or (thien van)) cham duc va hanh dai cua tre*.