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, hoc sach, doc sach
hieu ve » hieu va, hieu van
ve nhan » ve nha, de nhan, va nhan
nang o » nang co, nang ho, nang ro
vat va » dat va
va dai » va dao, vi dai, va dau
o hoi » co hoi, o hoc, o hai

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) or (toc san)) ky nang o 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) OR (toc san)) ky nang o 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) or (toc san)) ky nang o hoi. hieu ve nhan thuc vat va dai ((cua triet) OR (su triet))*".