Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
su sach » so sach, vu sach
co sach » bo sach, cuon sach, hoc sach
hieu ve » hieu va, hieu van
cac toc » cac toi, cac thoi
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
di su » doi su, ki su, da su

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) or (co sach)) ky nang x ho. hieu ve ((cac toc) OR (cac nuoc)) va hanh di su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (co sach)) ky nang x ho. hieu ve ((cac toc) OR (cac nuoc)) va hanh di su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (co sach)) ky nang x ho. hieu ve ((cac toc) OR (cac nuoc)) va hanh di su triet".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (co sach)) ky nang x ho. hieu ve ((cac toc) OR (cac nuoc)) va hanh di su triet*.