Perhaps you should try some spelling variations:
cua triet » cua viet, su triet
thanh lam » thanh lap, hanh lam, thanh nam
va triet » va thiet, va trien, ve triet
va thanh » gia thanh, ban thanh, va tinh
hieu van » hieu va, thien van, lieu va
cau duc » cao duc, cau luc, chu duc
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, 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 hai)). hieu van cau duc va thanh lam ((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 hai)). hieu van cau duc va thanh lam ((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 hai)). hieu van cau duc va thanh lam ((cua triet) OR (va triet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (o hai)). hieu van cau duc va thanh lam ((cua triet) OR (va triet))*.