Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
danh vai » danh sai, danh va, doanh van
hieu van » hieu va, thien van, lieu va
vai cua » dai cua, hai cua, lai cua
duoc va » duc va, duoc ma, duong va
van lam » van nam
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
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: ((te sach) or (toc sach)) ky lang xa hoi. hieu van lam ((duoc va) OR (nuoc va)) danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky lang xa hoi. hieu van lam ((duoc va) OR (nuoc va)) danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky lang xa hoi. hieu van lam ((duoc va) OR (nuoc va)) danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky lang xa hoi. hieu van lam ((duoc va) OR (nuoc va)) danh vai cua tre*.