Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
mai khoi » mai khoa, tai khoa, cac khoi
hanh doi » thanh doi, hanh noi, hang doi
va triet » va thiet, va trien, ve triet
mai hoi » dai hoi, lai hoi, mai doi
hieu ve » hieu va, hieu van
y tang » ky tang, 6 tang, 7 tang
luc va » duc va, tuc va
loc va » hoc va
doi va » hoi va, noi va, dai va
ve cau » ke cau, va cau, ve cac

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 y tang ((mai hoi) or (mai khoi)). hieu ve cau ((luc va) or (loc va)) hanh doi va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach y tang ((mai hoi) OR (mai khoi)). hieu ve cau ((luc va) OR (loc va)) hanh doi va triet.
• Adding a wildcard symbol may retrieve word variants: hoc sach y tang ((mai hoi) or (mai khoi)). hieu ve cau ((luc va) or (loc va)) hanh doi va triet*.