Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, lieu va
cau tren » cu tren, dau tren, ca tren
so sanh » do sanh
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
van cam » van nam, van lam, van cau
cam thu » nam thu, cac thu, ca thu
va hang » van hang, va nang, va lang
hang di » hang doi, hang vi, hang dien
thu va » thuc va, thue va, tu va
di cau » da cau, diem cau

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 van cam thu va hang di 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 van cam thu va hang di cau tren.
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) or (so sanh)) ky lang xa hoi. hieu van cam thu va hang di cau tren*.