Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
nang cai » nang cao, nang tai, nang cap
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
tang ma » mang may, tang van
qua cao » qua cac, qua ca, qua cai
cao duc » dao duc, cao suc, giao duc
van anh » tuan anh, van minh
cua tre » cua te, cuu tre, cua triet

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 ky ((nang cai) or (tang ma)) hoi. hieu qua cao duc ((van anh) OR (van thanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang cai) OR (tang ma)) hoi. hieu qua cao duc ((van anh) OR (van thanh)) dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang cai) or (tang ma)) hoi. hieu qua cao duc ((van anh) OR (van thanh)) dai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang cai) or (tang ma)) hoi. hieu qua cao duc ((van anh) OR (van thanh)) dai cua tre*.