Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
va cham » va chat, va tham
thi cua » thai cua, thi cuc, tri cua
ban thi » dan thi, van thi, can thi
quoc va » nuoc va, duoc va, quoc gia
va ban » van ban, va bai, va bao
tu san » thu san, tu ban, tu can
san ky » sang ky, van ky, dan ky
va cam » va cac, va cao, va cai
co hoi » co hoc, co loi
ro hoi » o hoi, mo hoi, ro doi

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 nang ((ro hoi) OR (co hoi)). hieu ((va cam) or (va cham)) quoc va ban thi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu san ky nang ((ro hoi) OR (co hoi)). hieu ((va cam) OR (va cham)) quoc va ban thi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu san ky nang ((ro hoi) OR (co hoi)). hieu ((va cam) or (va cham)) quoc va ban thi cua viet".
• Adding a wildcard symbol may retrieve word variants: tu san ky nang ((ro hoi) OR (co hoi)). hieu ((va cam) or (va cham)) quoc va ban thi cua viet*.