Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
doi nang » dai nang, hoi nang, voi nang
hieu van » hieu va, thien van, lieu va
su triet » su viet, su tien, ve triet
tu sach » thu sach, su sach, te sach
cao hoi » cau hoi, co hoi, tao hoi
cao hoc » co hoc, cho hoc, chat hoc
van cam » van nam, van lam, van cau
cam tuc » cam xuc, cam tu, nam thuc
va hanh » van hanh, va thanh, va danh
tuc va » thuc va, truc va, tuc xa
vi su » va su, ve su, ki su

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach doi nang ((cao hoi) or (cao hoc)). hieu van cam tuc va hanh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi nang ((cao hoi) OR (cao hoc)). hieu van cam tuc va hanh vi su triet.
• Adding a wildcard symbol may retrieve word variants: tu sach doi nang ((cao hoi) or (cao hoc)). hieu van cam tuc va hanh vi su triet*.