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

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