Perhaps you should try some spelling variations:
su triet » su tien, ve triet
thanh va » thanh van, hanh va, thanh ha
xa thanh » va thanh, ha thanh, ta thanh
tu sach » thu sach, su sach, te sach
cac tac » cac toc, cac bac, cac dac
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
ty nang » ky nang, ty xang, ty hang
su viet » so viet
ve cac » va cac, vien cac
tac xa » tuc xa, tac da
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 ty nang ((o hoi) OR (o hoc)). hieu ve cac tac xa thanh va ((su triet) or (su viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ((o hoi) OR (o hoc)). hieu ve cac tac xa thanh va ((su triet) OR (su viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty nang ((o hoi) OR (o hoc)). hieu ve cac tac xa thanh va ((su triet) or (su viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ((o hoi) OR (o hoc)). hieu ve cac tac xa thanh va ((su triet) or (su viet))*.