Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
hieu cac » hieu luc, hieu va, hieu van
hien cac » thien cac, vien cac, dien cac
va hanh » van hanh, va thanh, va danh
tu cach » tu cac
cach tu » cach thuc
lai hoi » dai hoi, lai hoa, lai roi
tu nang » tru nang, tu nong, tu nano
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu cach tu nang ((mai khoi) or (lai hoi)). hieu ((hien cac) OR (hieu cac)) duc va hanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu cach tu nang ((mai khoi) OR (lai hoi)). hieu ((hien cac) OR (hieu cac)) duc va hanh vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu cach tu nang ((mai khoi) or (lai hoi)). hieu ((hien cac) OR (hieu cac)) duc va hanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: tu cach tu nang ((mai khoi) or (lai hoi)). hieu ((hien cac) OR (hieu cac)) duc va hanh vi cua vat*.