Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
thanh vi » hanh vi, thanh va, thanh ve
xa thanh » va thanh, ha thanh, ta thanh
sach ky » sac ky, sach y, sach ty
cac toc » cac toi, cac nuoc, cac thoi
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
cac tuc » cac tu, cac tac, cac nuoc
o hoc » mo hoc, so hoc, y hoc
vi su » va su, ve su, ki su

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 hoc) OR (co hoc)). hieu ve ((cac tuc) or (cac toc)) xa thanh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoc) OR (co hoc)). hieu ve ((cac tuc) OR (cac toc)) xa thanh vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoc) OR (co hoc)). hieu ve ((cac tuc) or (cac toc)) xa thanh vi su triet".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoc) OR (co hoc)). hieu ve ((cac tuc) or (cac toc)) xa thanh vi su triet*.