Perhaps you should try some spelling variations:
thanh ca » thanh cha, thanh cac, thanh ha
so sach » so sanh, bo sach, co sach
duc van » duc va, duc tan, duc manh
duc ban » duc tan, dua ban, duc man
cua tre » cua te, cuu tre, cua triet
ky dang » ky nang, ky danh
ky sang » ky nang, ky tang, duy sang
ma hoi » mai hoi, xa hoi, ma hoa
ca cua » co cua
va lam » van lam, va lap

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 sang) or (ky dang)) ma hoi. lieu va lam ((duc ban) OR (duc van)) thanh ca cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((ky sang) OR (ky dang)) ma hoi. lieu va lam ((duc ban) OR (duc van)) thanh ca cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((ky sang) or (ky dang)) ma hoi. lieu va lam ((duc ban) OR (duc van)) thanh ca cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ((ky sang) or (ky dang)) ma hoi. lieu va lam ((duc ban) OR (duc van)) thanh ca cua tre*.