Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
hoc sach » hoc sinh, hoc cac, hoc anh
cau thuc » cau truc, cuu thuc, can thuc
dau tren » dau tien, dat tren, dau tieng
sach ky » sac ky, sach y, sach ty
mai hoi » dai hoi, lai hoi, mai doi
hieu ve » hieu va, hieu van
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
danh vi » hanh vi, dinh vi, danh di
ve cau » ke cau, va cau, ve cac
vi dau » vi dai, va dau, bi dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ky nang ((xa hoi) or (((mai hoi) OR (mai khoi)))). hieu ve cau thuc va danh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ky nang ((xa hoi) OR (((mai hoi) OR (mai khoi)))). hieu ve cau thuc va danh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ky nang ((xa hoi) or (((mai hoi) OR (mai khoi)))). hieu ve cau thuc va danh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: hoc sach ky nang ((xa hoi) or (((mai hoi) OR (mai khoi)))). hieu ve cau thuc va danh vi dau tren*.