Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
sach thue » sach thu, sach thieu, sach tham
dang xay » dang van, van xay
nam thuc » nam thuoc, am thuc, nam tu
su sach » so sach, vu sach
lang xa » lang ha, lang van
va doan » va doanh, van doan, va dan
cua tre » cua te, cuu tre, cua triet
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: su sach thue ((lang xa) or (dang xay)) hoi. hieu quang ((nam thuc) OR (nam thu)) va doan va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach thue ((lang xa) OR (dang xay)) hoi. hieu quang ((nam thuc) OR (nam thu)) va doan va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach thue ((lang xa) or (dang xay)) hoi. hieu quang ((nam thuc) OR (nam thu)) va doan va cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach thue ((lang xa) or (dang xay)) hoi. hieu quang ((nam thuc) OR (nam thu)) va doan va cua tre*.