Perhaps you should try some spelling variations:
su triet » su viet, ve triet
thanh vi » hanh vi, thanh va, thanh ve
cac quoc » cac nuoc, cac cuoc, cao quoc
qua cac » cua cac
su sach » so sach, vu sach
mai hoi » mai khoi, dai hoi, lai hoi
ly hang » ly quang
ty hang » ty xang, thi hang, thu hang
su tien » su kien, su hien, tu tieng
gia » giao

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 ((ty hang) or (ly hang)) mai hoi. hieu qua cac quoc gia thanh vi ((su triet) OR (su tien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty hang) OR (ly hang)) mai hoi. hieu qua cac quoc gia thanh vi ((su triet) OR (su tien)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty hang) or (ly hang)) mai hoi. hieu qua cac quoc gia thanh vi ((su triet) OR (su tien))".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty hang) or (ly hang)) mai hoi. hieu qua cac quoc gia thanh vi ((su triet) OR (su tien))*.