Perhaps you should try some spelling variations:
sach thi » sach thu, sach thieu, sach tham
sach tai » sach bai, sach tham, sach dao
duc phan » dung phan, duc thang, duc phung
hieu ve » hieu va, hieu van
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
hang o » hang do, hang o2, hoang o
ve cac » va cac, vien cac
di cua » dai cua, doi cua, de cua
o hoi » co hoi, o hoc, o hai

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 thi) OR (sach tai)) hang o hoi. hieu ve cac ((duc phan) or (duc va)) hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach thi) OR (sach tai)) hang o hoi. hieu ve cac ((duc phan) OR (duc va)) hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach thi) OR (sach tai)) hang o hoi. hieu ve cac ((duc phan) or (duc va)) hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach thi) OR (sach tai)) hang o hoi. hieu ve cac ((duc phan) or (duc va)) hanh di cua tre*.