Perhaps you should try some spelling variations:
cua triet » cua viet, va triet
nhan thuc » nhan luc, dan thuc, toan thuc
su triet » su viet, su tien, ve triet
toc sac » toc sach, toc san, hoc sach
hieu ve » hieu va, hieu van
ve nhan » ve nha, de nhan, va nhan
sac ky » cac ky, sai ky
co hoi » co hoc, co loi
vat va » dat va
va dai » va dao, vi dai, va dau
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: toc sac ky nang ((o hoi) or (co hoi)). hieu ve nhan thuc vat va dai ((cua triet) OR (su triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sac ky nang ((o hoi) OR (co hoi)). hieu ve nhan thuc vat va dai ((cua triet) OR (su triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sac ky nang ((o hoi) or (co hoi)). hieu ve nhan thuc vat va dai ((cua triet) OR (su triet))".
• Adding a wildcard symbol may retrieve word variants: toc sac ky nang ((o hoi) or (co hoi)). hieu ve nhan thuc vat va dai ((cua triet) OR (su triet))*.