Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh vai » hanh vi, hanh va, hanh tai
vai cua » dai cua, hai cua, lai cua
duoc xa » duoc ma, duoc va, duoc ha
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
nong xa » song xa, dong xa, nong va
tu nong » tu dong, tu cong, tu tong
duc xa » tuc xa, duc va, duc ha
va cao » va cac, va co, va dao

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) tu nong xa hoi. hieu va cao ((duc xa) OR (duoc xa)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) tu nong xa hoi. hieu va cao ((duc xa) OR (duoc xa)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) tu nong xa hoi. hieu va cao ((duc xa) OR (duoc xa)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) tu nong xa hoi. hieu va cao ((duc xa) OR (duoc xa)) hanh vai cua tre*.