Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
dang xay » dang van, van xay
thanh di » thanh doi, thanh de, thanh do
co viet » so viet, o viet, hoc viet
ky dang » ky nang, ky danh
xay hoi » xa hoi, tay hoi, cay phoi
ca viet » va viet, hoa viet, san viet
cua duc » cua tuc, cua nuoc, cua quoc
tu san » thu san, tu ban, tu can
san ky » sang ky, van ky, dan ky
ca duc » cao duc, ca dua, ha duc

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu san ky dang xay hoi. hieu qua ((ca duc) or (cua duc)) van thanh di ((ca viet) OR (co viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu san ky dang xay hoi. hieu qua ((ca duc) OR (cua duc)) van thanh di ((ca viet) OR (co viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu san ky dang xay hoi. hieu qua ((ca duc) or (cua duc)) van thanh di ((ca viet) OR (co viet))".
• Adding a wildcard symbol may retrieve word variants: tu san ky dang xay hoi. hieu qua ((ca duc) or (cua duc)) van thanh di ((ca viet) OR (co viet))*.