Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, lanh dao
thi hanh » thi thanh
hanh cau » nhanh cau, hang cau, hanh cac
hieu cao » chieu cao, hieu ca, kieu cao
su triet » su viet, su tien, ve triet
hieu cac » hieu luc, hieu va, hieu van
sach thi » sach thu, sach tai, sach thieu
chat tuc » chat xuc, luat tuc, chat huu
tu sach » thu sach, su sach, te sach
so viet » hoc viet
va vanh » va van, va hanh, va danh
tuc va » thuc va, truc va, tuc xa

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 thi hanh cau hoi. ((hieu cao) OR (hieu cac)) chat tuc va vanh dai ((su triet) or (so viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach thi hanh cau hoi. ((hieu cao) OR (hieu cac)) chat tuc va vanh dai ((su triet) OR (so viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach thi hanh cau hoi. ((hieu cao) OR (hieu cac)) chat tuc va vanh dai ((su triet) or (so viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach thi hanh cau hoi. ((hieu cao) OR (hieu cac)) chat tuc va vanh dai ((su triet) or (so viet))*.