Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
ty lang » tay lang, ty xang, ty hang
lang xa » lang ha, dang xay, lang van
van cau » van dau, van hau, van chat
cua tre » cua te, cuu tre, cua triet
tuc va » thuc va, truc va, tuc xa
va cua » va chua, via cua, ca cua

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 van cau ((tuc va) or (duc va)) hang va 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 van cau ((tuc va) OR (duc va)) hang va 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 van cau ((tuc va) or (duc va)) hang va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ty lang xa hoi. hieu van cau ((tuc va) or (duc va)) hang va cua tre*.