Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
cau tren » cu tren, dau tren, ca tren
danh vi » hanh vi, dinh vi, danh di
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky nang, ky dang, ky tang
sach ky » sac ky, sach y, sach ty
va danh » va dinh, va dan, va hanh
vi cau » di cau, viet cau
luc va » duc va, tuc va, loc va
ve cau » ke cau, ve cac, le cau
va cau » van cau, va cac, va dau
ma hoi » xa hoi, ma hoa, me hoi

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