Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, sach tham
sach ty » sach y, sach tu, xach tay
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
duc ban » duc tan, duc van, dua ban
nang o » nang co, nang ho, nang ro
lam su » lam so, lam vu
o hoi » co hoi, o hoc, o hai

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach ty) OR (sach thu)) nang o hoi. hieu van cau duc ban thanh ((lam su) or (lai su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) nang o hoi. hieu van cau duc ban thanh ((lam su) OR (lai su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ty) OR (sach thu)) nang o hoi. hieu van cau duc ban thanh ((lam su) or (lai su)) triet".
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) OR (sach thu)) nang o hoi. hieu van cau duc ban thanh ((lam su) or (lai su)) triet*.