Perhaps you should try some spelling variations:
nam thuc » nam thuoc, nam thu, nam tu
dinh tai » dinh toai, dinh tri, dinh thi
tu sach » thu sach, su sach, te sach
nang xa » lang xa, nang ma, mang xa
hieu ve » hieu va, hieu van
va dinh » van dinh, va kinh, va tinh
cuc tre » duc tre, cua tre, cuu tre

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach y ((nang xa) or (nang x)) hoi. hieu ve ((nam thuc) OR (am thuc)) va dinh tai cuc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang xa) OR (nang x)) hoi. hieu ve ((nam thuc) OR (am thuc)) va dinh tai cuc tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang xa) or (nang x)) hoi. hieu ve ((nam thuc) OR (am thuc)) va dinh tai cuc tre*".