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

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 hanh vai ((cua viet) OR (hoa 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 hanh vai ((cua viet) OR (hoa 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 hanh vai ((cua viet) OR (hoa viet))".
• Adding a wildcard symbol may retrieve word variants: so sach v nang ((mai hoi) or (mai khoi)). hieu ve cam thuc va hanh vai ((cua viet) OR (hoa viet))*.