Perhaps you should try some spelling variations:
sach tham » sach nha
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, cach thuc
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
xang xa » lang xa, mang xa, ang xa
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach thu) OR (sach tham)) xang xa hoi. hieu van cac ((xac va) or (tuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach thu) OR (sach tham)) xang xa hoi. hieu van cac ((xac va) OR (tuc va)) hanh vi cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach thu) OR (sach tham)) xang xa hoi. hieu van cac ((xac va) or (tuc va)) hanh vi cua tre*".