Perhaps you should try some spelling variations:
toc sach » hoc sach, thuoc sach, nuoc sach
doc sach » hoc sach, nuoc sach, dac sac
nam thuc » nam thuoc, am thuc, nam thu
dan vai » dan tai, dan vat, den vai
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
cuu tre » cua tre, cau tren, cau treo
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
dan va » doan va, dan ca, ban va
va nam » van nam, ha nam, va nay

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

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