Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu qua, diep quang
hieu quan » hieu qua, lieu quan, thien quan
nam thuc » nam thuoc, am thuc, nam thu
dang xay » dang van, van xay
su sach » so sach, vu sach
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
sach ty » sach y, sach tu, sach thu
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: su sach ty ((lang xa) or (dang xay)) hoi. ((hieu quang) OR (hieu quan)) nam thuc va dan vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((lang xa) OR (dang xay)) hoi. ((hieu quang) OR (hieu quan)) nam thuc va dan vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ((lang xa) or (dang xay)) hoi. ((hieu quang) OR (hieu quan)) nam thuc va dan vai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((lang xa) or (dang xay)) hoi. ((hieu quang) OR (hieu quan)) nam thuc va dan vai cua tre*.