Perhaps you should try some spelling variations:
hieu ve » hieu va, hieu van
cao duc » dao duc, cao suc, giao duc
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
ve cao » va cao, ve bao, ve cac
di cua » dai cua, doi cua, de cua
x hoi » xa hoi, o hoi, 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 y) or (sac ky)) nang ((x hoi) OR (x ho)). hieu ve cao duc va hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach y) OR (sac ky)) nang ((x hoi) OR (x ho)). hieu ve cao duc va hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach y) or (sac ky)) nang ((x hoi) OR (x ho)). hieu ve cao duc va hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach y) or (sac ky)) nang ((x hoi) OR (x ho)). hieu ve cao duc va hanh di cua tre*.