Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
tu sach » thu sach, su sach, te sach
doan do » doan o, toan do, doanh dao
cuc ban » cua ban, cac ban, cuu ban
cam cuc » cam xuc, cham cuu, pham cuc
cuu tre » cua tre, cau tren, cau treo
hieu va » lieu va, hieu qua
co hoi » co hoc, co loi
dan do » dang do, dan dao, ban do
va cam » va cham, va cac, va cao
o hoi » o hoc, o hai, o hoa

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 thu nang ((o hoi) OR (co hoi)). hieu va cam cuc ban ((dan do) or (doan do)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu nang ((o hoi) OR (co hoi)). hieu va cam cuc ban ((dan do) OR (doan do)) cuu tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thu nang ((o hoi) OR (co hoi)). hieu va cam cuc ban ((dan do) or (doan do)) cuu tre*".