Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
cua viet » ca viet, hoa viet, cua vat
so sach » so sanh, bo sach, co sach
sach ty » sach y, sach tu, sach thu
ty tang » tay tang, ty xang, ty hang
hieu he » hieu ve, hiem he, hieu le
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
ma hoi » mai hoi, ma hoa, me hoi
he nam » ha nam, nghe nam
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: so sach ty tang ((ma hoi) or (xa hoi)). hieu he nam thuc va hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty tang ((ma hoi) OR (xa hoi)). hieu he nam thuc va hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: so sach ty tang ((ma hoi) or (xa hoi)). hieu he nam thuc va hanh vi cua viet*.