Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
nuoc sach » nguoi sach, hoc sach, cuoc cach
hieu cua » hieu qua, dieu cua, bieu cua
va thanh » gia thanh, va tinh, le thanh
ty hang » ly hang, thi hang, thu hang
ca viet » va viet, co viet, hoa viet
cac bo » bac bo, cac co
tai ca » tai cac, tai cao, tai cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: nuoc sach ((ty hang) or (ty xang)) xa hoi. hieu cua cac bo ((va thanh) OR (ban thanh)) tai ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: nuoc sach ((ty hang) OR (ty xang)) xa hoi. hieu cua cac bo ((va thanh) OR (ban thanh)) tai ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "nuoc sach ((ty hang) or (ty xang)) xa hoi. hieu cua cac bo ((va thanh) OR (ban thanh)) tai ca viet".
• Adding a wildcard symbol may retrieve word variants: nuoc sach ((ty hang) or (ty xang)) xa hoi. hieu cua cac bo ((va thanh) OR (ban thanh)) tai ca viet*.