Perhaps you should try some spelling variations:
cua triet » cua viet, su triet
va triet » va thiet, va trien, ve triet
tinh dai » trinh dai, tinh da, tinh hai
va tinh » may tinh
cao duc » dao duc, cao suc, giao duc
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
va cao » va cac, va co, va dao
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, 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 ky nang ((o hoi) OR (o hoc)). hieu va cao duc va tinh dai ((cua triet) or (va triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hoc)). hieu va cao duc va tinh dai ((cua triet) OR (va triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) OR (o hoc)). hieu va cao duc va tinh dai ((cua triet) or (va triet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) OR (o hoc)). hieu va cao duc va tinh dai ((cua triet) or (va triet))*.