Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
diem cau » dieu can
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
so sanh » do sanh
hieu ve » hieu va, hieu van
cam thu » nam thu, cac thu, ca thu
va hang » van hang, va nang, va lang
thu va » thuc va, thue va, tu va
di cau » da cau
ve cam » ve cham, ve cac, va cam

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) or (so sanh)) ky lang xa hoi. hieu ve cam thu va hang ((di cau) OR (diem cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (so sanh)) ky lang xa hoi. hieu ve cam thu va hang ((di cau) OR (diem cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) or (so sanh)) ky lang xa hoi. hieu ve cam thu va hang ((di cau) OR (diem cau)) tren".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (so sanh)) ky lang xa hoi. hieu ve cam thu va hang ((di cau) OR (diem cau)) tren*.