Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
nam thuoc » nam thu, nha thuoc, cay thuoc
nam thuc » am thuc, nam thu, nam tu
dang xay » dang van, van xay
vat cua » mat cua, bat cua, dat cua
dan vat » dang vat, van vat, dan va
so sach » so sanh, bo sach, co sach
lang xa » lang ha, lang van
cua tre » cua te, cuu tre, cua triet
va dan » ca dan, va dao, va dau

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

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