Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
danh vai » danh sai, danh va, doanh van
vai cua » dai cua, hai cua, lai cua
hieu va » lieu va, hieu qua
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
xac va » tac va, ac va, bac va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) ty lang xa hoi. hieu va cam ((xac va) or (duc va)) danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ty lang xa hoi. hieu va cam ((xac va) OR (duc va)) danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ty lang xa hoi. hieu va cam ((xac va) or (duc va)) danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ty lang xa hoi. hieu va cam ((xac va) or (duc va)) danh vai cua tre*.