Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
so sach » bo sach, co sach, hoc sach
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu ve » hieu va
so sanh » do sanh
sang ma » tang ma, nang ma, sang tao
ca viet » va viet, co viet, hoa viet
ma hoi » mai hoi, xa hoi, ma hoa
y sang » _ sang, duy sang
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) OR (so sanh)) y sang ma hoi. ((hieu ve) or (hieu van)) am thuc va hanh vi ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sach) OR (so sanh)) y sang ma hoi. ((hieu ve) OR (hieu van)) am thuc va hanh vi ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sach) OR (so sanh)) y sang ma hoi. ((hieu ve) or (hieu van)) am thuc va hanh vi ca viet".
• Adding a wildcard symbol may retrieve word variants: ((so sach) OR (so sanh)) y sang ma hoi. ((hieu ve) or (hieu van)) am thuc va hanh vi ca viet*.