Perhaps you should try some spelling variations:
cua triet » su triet, va triet
hieu vien » hieu hien, hieu viec, thieu nien
cua viet » ca viet, hoa viet, cua vat
ban hanh » ban hang
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hanh di » hanh vi, hanh de, hang di
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
cac toc » cac toi, cac thoi
nang xa » nang x, lang xa, nang ma

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang xa hoi. hieu vien ((cac toc) OR (cac nuoc)) ban hanh di ((cua triet) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang xa hoi. hieu vien ((cac toc) OR (cac nuoc)) ban hanh di ((cua triet) OR (cua viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang xa hoi. hieu vien ((cac toc) OR (cac nuoc)) ban hanh di ((cua triet) or (cua viet))".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang xa hoi. hieu vien ((cac toc) OR (cac nuoc)) ban hanh di ((cua triet) or (cua viet))*.