Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van anh
va trien » va truyen, va thiet, va tuyen
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
ma hoi » mai hoi, xa hoi, me hoi
vi va » vi van, vai va, vu va

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ty xang ((ma hoi) OR (ma hoa)). hieu ve ((nam thuc) or (cam xuc)) van hanh vi va trien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty xang ((ma hoi) OR (ma hoa)). hieu ve ((nam thuc) OR (cam xuc)) van hanh vi va trien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty xang ((ma hoi) OR (ma hoa)). hieu ve ((nam thuc) or (cam xuc)) van hanh vi va trien".
• Adding a wildcard symbol may retrieve word variants: su sach ty xang ((ma hoi) OR (ma hoa)). hieu ve ((nam thuc) or (cam xuc)) van hanh vi va trien*.