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