Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
cua viet » ca viet, hoa viet, cua vat
va thanh » gia thanh, ban thanh, va tinh
sach tu » sach thu, cach tu, sach uu
sach ty » sach y, sach thu, xach tay
cao duc » dao duc, cao suc, giao duc
cua tre » cua te, cuu tre, cua triet
xang o » lang o, tang o, dang o
va cao » va cac, va co, va dao
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: su ((sach ty) OR (sach tu)) xang o hoi. lieu va cao duc va thanh vai ((cua tre) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach tu)) xang o hoi. lieu va cao duc va thanh vai ((cua tre) OR (cua viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach tu)) xang o hoi. lieu va cao duc va thanh vai ((cua tre) or (cua viet))".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach tu)) xang o hoi. lieu va cao duc va thanh vai ((cua tre) or (cua viet))*.