Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
va viet » hoa viet, san viet, mai viet
duc ban » duc tan, duc van, dua ban
hang di » hang doi, hang vi, hang dien
hanh di » hanh vi, hanh de, danh di
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
ca duc » cao duc, cua duc, ca dua
qua ca » qua cac, qua cua, qua cai
san ky » sang ky, van ky, dan ky
tu san » thu san, tu ban, tu can

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 tang xa hoi. hieu qua ca duc ban ((hanh di) OR (hang di)) ((cua viet) or (va viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu san ky tang xa hoi. hieu qua ca duc ban ((hanh di) OR (hang di)) ((cua viet) OR (va viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu san ky tang xa hoi. hieu qua ca duc ban ((hanh di) OR (hang di)) ((cua viet) or (va viet))".
• Adding a wildcard symbol may retrieve word variants: tu san ky tang xa hoi. hieu qua ca duc ban ((hanh di) OR (hang di)) ((cua viet) or (va viet))*.