Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
hieu van » hieu va, thien van, lieu va
mai hoi » dai hoi, lai hoi, mai doi
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
vai cua » dai cua, hai cua, lai cua
vu sac » vu sach, vu san, va sac
sac ky » cac ky, sai ky
van am » van nam, van lam, van dam
vi 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: vu sac ky nang ((mai hoi) or (mai khoi)). hieu van am thuc va hanh ((vi cua) OR (vai cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sac ky nang ((mai hoi) OR (mai khoi)). hieu van am thuc va hanh ((vi cua) OR (vai cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sac ky nang ((mai hoi) or (mai khoi)). hieu van am thuc va hanh ((vi cua) OR (vai cua)) te".
• Adding a wildcard symbol may retrieve word variants: vu sac ky nang ((mai hoi) or (mai khoi)). hieu van am thuc va hanh ((vi cua) OR (vai cua)) te*.