Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
ky lang » ky dang, ky tang, tay lang
van cam » van nam, van lam, van cau
duc ban » duc van, dua ban, duc man
vai cua » dai cua, hai cua, lai cua
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: thu sach ((ky lang) OR (ky nang)) xa hoi. hieu van cam ((duc ban) or (duc tan)) thanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky lang) OR (ky nang)) xa hoi. hieu van cam ((duc ban) OR (duc tan)) thanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky lang) OR (ky nang)) xa hoi. hieu van cam ((duc ban) or (duc tan)) thanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky lang) OR (ky nang)) xa hoi. hieu van cam ((duc ban) or (duc tan)) thanh vai cua tre*.