Perhaps you should try some spelling variations:
va thieu » va thiet, va hieu, va tieu
va triet » va thiet, va trien, ve triet
hanh vai » hanh vi, hanh va, hanh tai
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
tang ma » mang may, tang van
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
sang ma » nang ma, sang tao, mang may
co sach » bo sach, cuon sach, hoc sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach y ((sang ma) or (tang ma)) hoi. hieu van nam thuc va hanh vai ((va triet) or (va thieu))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach y ((sang ma) OR (tang ma)) hoi. hieu van nam thuc va hanh vai ((va triet) OR (va thieu)).
• Adding a wildcard symbol may retrieve word variants: co sach y ((sang ma) or (tang ma)) hoi. hieu van nam thuc va hanh vai ((va triet) or (va thieu))*.