Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
dang xay » dang van, van xay
su sach » so sach, vu sach
cam tuc » cam xuc, cam tu, dam thuc
sach ty » sach y, sach tu, sach thu
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, nang ma
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 ((nang xa) or (dang xay)) hoi. hieu va ((cam tuc) OR (nam thuc)) va dan vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((nang xa) OR (dang xay)) hoi. hieu va ((cam tuc) OR (nam 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 ((cam tuc) OR (nam 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 ((cam tuc) OR (nam thuc)) va dan vi cua tre*.