Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
ban hang » ngan hang
nam duoc » nam thuoc, da duoc, dat duoc
so sach » so sanh, bo sach, co sach
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
ky tang » ky nang, ky dang, kho tang
ma hoi » mai hoi, xa hoi, ma hoa

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 ky tang ma hoi. hieu ve ((nam duoc) or (pham duc)) ((van thanh) or (ban hang)) hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky tang ma hoi. hieu ve ((nam duoc) OR (pham duc)) ((van thanh) OR (ban hang)) hai cua tre.
• Adding a wildcard symbol may retrieve word variants: so sach ky tang ma hoi. hieu ve ((nam duoc) or (pham duc)) ((van thanh) or (ban hang)) hai cua tre*.