Perhaps you should try some spelling variations:
nhanh thi » nhanh thai, nhanh thuc, nhan tai
van nhanh » van thanh, van hanh, van khanh
thu nang » thi nang, thu hang, thu bang
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, sach tham
tu sach » thu sach, su sach, te sach
cao duc » dao duc, cao suc, giao duc
thi cua » thai cua, thi cuc, tri cua
cau duc » cau luc, chu duc, cau truc
cua tre » cua te, cuu tre, cua triet
co hoi » co hoc, co loi
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 van ((cau duc) OR (cao duc)) van nhanh thi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thu nang ((o hoi) OR (co hoi)). hieu van ((cau duc) OR (cao duc)) van nhanh thi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thu nang ((o hoi) or (co hoi)). hieu van ((cau duc) OR (cao duc)) van nhanh thi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach thu nang ((o hoi) or (co hoi)). hieu van ((cau duc) OR (cao duc)) van nhanh thi cua tre*.