Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
sach tru » sach truc, sach thu, sach tu
va danh » va dinh, va hanh, dia danh
qua cao » qua cac, qua ca, qua cai
lang xa » lang ha, lang van
va dan » ca dan, va dao, va dau
va cua » va chua, via cua, ca cua
cua te » cua tu

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 tru ((lang xa) or (dang xay)) hoi. hieu qua cao su ((va danh) OR (va dan)) va cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach tru ((lang xa) OR (dang xay)) hoi. hieu qua cao su ((va danh) OR (va dan)) va cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach tru ((lang xa) or (dang xay)) hoi. hieu qua cao su ((va danh) OR (va dan)) va cua te".
• Adding a wildcard symbol may retrieve word variants: toc sach tru ((lang xa) or (dang xay)) hoi. hieu qua cao su ((va danh) OR (va dan)) va cua te*.