Perhaps you should try some spelling variations:
dang xay » dang van, van xay
nam thuc » nam thuoc, nam thu, nam tu
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
nang xa » nang x, lang xa, nang ma
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.

• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((nang xa) OR (dang xay)) hoi. hieu va ((nam thuc) OR (am thuc)) va dan vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ((nang xa) or (dang xay)) hoi. hieu va ((nam thuc) OR (am thuc)) va dan vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((nang xa) or (dang xay)) hoi. hieu va ((nam thuc) OR (am thuc)) va dan vi cua tre*.