Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
so sach » so sanh, bo sach, co sach
sach ty » sach y, sach tu, sach thu
hieu le » hieu ve, hieu he, hieu ly
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
ca viet » va viet, co viet, hoa viet
ma hoi » mai hoi, ma hoa, me hoi
le nam » ly nam, he nam, le na
vi ca » vit ca, li ca, va ca

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty xang ((ma hoi) or (xa hoi)). hieu le nam thuc va hanh vi ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty xang ((ma hoi) OR (xa hoi)). hieu le nam thuc va hanh vi ca viet.
• Adding a wildcard symbol may retrieve word variants: so sach ty xang ((ma hoi) or (xa hoi)). hieu le nam thuc va hanh vi ca viet*.