Perhaps you should try some spelling variations:
su triet » su tien, ve triet
thanh va » thanh van, hanh va, thanh ha
va thanh » gia thanh, ban thanh, va tinh
truc va » thuc va, thuc vat, trung va
sach ty » sach y, sach thu, xach tay
hieu ve » hieu va, hieu van
sach tu » sach thu, cach tu, sach uu
su viet » so viet
ve cau » ke cau, va cau, ve 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: so ((sach ty) or (sach tu)) xang o hoi. hieu ve cau truc va thanh va ((su triet) OR (su viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach tu)) xang o hoi. hieu ve cau truc va thanh va ((su triet) OR (su viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ty) or (sach tu)) xang o hoi. hieu ve cau truc va thanh va ((su triet) OR (su viet))".
• Adding a wildcard symbol may retrieve word variants: so ((sach ty) or (sach tu)) xang o hoi. hieu ve cau truc va thanh va ((su triet) OR (su viet))*.