Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
su triet » su viet, su tien, ve triet
sach ky » sac ky, sach y, sach ty
cac toc » cac toi, cac nuoc, cac thoi
tu sach » thu sach, su sach, te sach
cac tuc » cac tu, cac tac, cac nuoc
hieu ve » hieu va, hieu van
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh
tai su » tai so, tai tu, lai su

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