Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
thanh de » hanh de, thanh ve, thanh do
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
dua van » duy van, dua vao, dua ban
duc van » duc va, duc tan, duc manh
cua tre » cua te, cuu tre, cua triet
va hoc » van hoc
de cua » le cua, te cua, dieu cua
x hoi » o hoi, x ho, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ty xang ((x hoi) or (xa hoi)). hieu va hoc ((dua van) OR (duc van)) thanh de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ty xang ((x hoi) OR (xa hoi)). hieu va hoc ((dua van) OR (duc van)) thanh de cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ty xang ((x hoi) or (xa hoi)). hieu va hoc ((dua van) OR (duc van)) thanh de cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ty xang ((x hoi) or (xa hoi)). hieu va hoc ((dua van) OR (duc van)) thanh de cua tre*.