Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
hanh vai » hanh vi, hanh va, hanh tai
thuc dan » thuc hanh, hoc dan, thuc vat
mai khoi » mai khoa, tai khoa, cac khoi
vai cua » dai cua, hai cua, lai cua
thuc va » thuc vat, thuc day
so sach » so sanh, bo sach, co sach
mai hoi » dai hoi, lai hoi, mai doi
hieu ve » hieu va, hieu van
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
ve cam » ve cham, ve cac, va cam

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 v nang ((mai hoi) or (mai khoi)). hieu ve cam ((thuc va) OR (thuc dan)) hanh vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach v nang ((mai hoi) OR (mai khoi)). hieu ve cam ((thuc va) OR (thuc dan)) hanh vai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach v nang ((mai hoi) or (mai khoi)). hieu ve cam ((thuc va) OR (thuc dan)) hanh vai cua viet".
• Adding a wildcard symbol may retrieve word variants: so sach v nang ((mai hoi) or (mai khoi)). hieu ve cam ((thuc va) OR (thuc dan)) hanh vai cua viet*.