Perhaps you should try some spelling variations:
su triet » su viet, ve triet
ban hanh » ban hang
hieu van » hieu va, thien van, lieu va
thu sac » thu sach, thu san, thu xac
cam ban » can ban, cac ban, cam bay
hanh di » hanh vi, hanh de, hang di
cac cam » cad cam, cac cap, cac cau
van cac » van hac, van cau, van bac
nang xa » nang x, lang xa, nang ma
su tien » su kien, su hien, tu tieng
sac ky » cac ky, sai ky

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

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