Perhaps you should try some spelling variations:
cua triet » cua viet, va triet
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
su triet » su viet, su tien, ve triet
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ho » nang hoc, nang co, tang ho
nang o » nang co, nang ro, nang x
ban bo » can bo, ban do, ban co
bo van » vo van, so van, do van

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 ky ((nang o) OR (nang ho)) hoi. hieu van ban bo van hanh vi ((cua triet) or (su triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang o) OR (nang ho)) hoi. hieu van ban bo van hanh vi ((cua triet) OR (su triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang o) OR (nang ho)) hoi. hieu van ban bo van hanh vi ((cua triet) or (su triet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang o) OR (nang ho)) hoi. hieu van ban bo van hanh vi ((cua triet) or (su triet))*.