Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
thanh va » thanh van, hanh va, thanh ha
thanh vi » hanh vi, thanh ve, nhanh vi
nuoc ha » nuoc va, ngoc ha, nuoc ta
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
ly vang » ly hang, ly quang
ly van » le van, ly va, ly von
ve cac » va cac, vien cac

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 ((ly vang) or (ly van)) xa hoi. hieu ve cac nuoc ha ((thanh vi) OR (thanh va)) su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((ly vang) OR (ly van)) xa hoi. hieu ve cac nuoc ha ((thanh vi) OR (thanh va)) su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((ly vang) or (ly van)) xa hoi. hieu ve cac nuoc ha ((thanh vi) OR (thanh va)) su triet".
• Adding a wildcard symbol may retrieve word variants: so sach ((ly vang) or (ly van)) xa hoi. hieu ve cac nuoc ha ((thanh vi) OR (thanh va)) su triet*.