Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
van hanh » van thanh, ban hanh, van anh
cac toc » cac toi, cac nuoc, cac thoi
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cac tuc » cac tu, cac tac, cac nuoc
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
vai va » dai va, hai va, lai va

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 ky lang xa hoi. hieu vien ((cac tuc) or (cac toc)) van hanh ((vai va) OR (mai va)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky lang xa hoi. hieu vien ((cac tuc) OR (cac toc)) van hanh ((vai va) OR (mai va)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky lang xa hoi. hieu vien ((cac tuc) or (cac toc)) van hanh ((vai va) OR (mai va)) triet".
• Adding a wildcard symbol may retrieve word variants: su sach ky lang xa hoi. hieu vien ((cac tuc) or (cac toc)) van hanh ((vai va) OR (mai va)) triet*.