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