Perhaps you should try some spelling variations:
danh vai » danh sai, danh va, doanh van
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
va danh » va dinh, va dan, va hanh
cau duc » cao duc, cau luc, chu duc
hieu va » hieu qua
cua tre » cua te, cuu tre, cua triet
le lang » le tang, le dang, le xang
ly lang » ly hang, ly vang, ly lanh

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 ((ly lang) OR (le lang)) xa hoi. ((lieu va) or (hieu va)) cau duc va danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ly lang) OR (le lang)) xa hoi. ((lieu va) OR (hieu va)) cau duc va danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ly lang) OR (le lang)) xa hoi. ((lieu va) or (hieu va)) cau duc va danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ly lang) OR (le lang)) xa hoi. ((lieu va) or (hieu va)) cau duc va danh vai cua tre*.