Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
mai hoi » dai hoi, lai hoi, mai doi
bac dai » bach mai
va hanh » van hanh, va thanh, va danh
ma hoi » xa hoi, ma hoa, me hoi
va bac » van bac, va cac, va bai
dai va » mai va
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 sach ky nang ((ma hoi) or (((mai hoi) OR (mai khoi)))). lieu va bac dai va hanh vi cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((ma hoi) OR (((mai hoi) OR (mai khoi)))). lieu va bac dai va hanh vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((ma hoi) or (((mai hoi) OR (mai khoi)))). lieu va bac dai va hanh vi cua vat".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((ma hoi) or (((mai hoi) OR (mai khoi)))). lieu va bac dai va hanh vi cua vat*.