Perhaps you should try some spelling variations:
trinh cham » trinh han, trinh phan, trinh cau
trinh chat » tinh chat, trinh luat, trinh han
trinh chao » trinh han, trinh co, trinh giao
choi viet » cuoi viet, chi viet, thoai viet
hoi viet » hai viet, oi viet, thai viet
doanh va » doan va, doanh tai, doanh cua
cot soi » cot loi, cong soi
tao cao » bao cao, toan cao
lanh va » hanh va, anh va, lanh dao
cac tap » cac cap, cac tac, cac tai
dao cao » dao tao, bao cao, do cao
cap do » cau do
co soi » co so, co hoi, co loi

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( cong trinh cham ((lanh va) OR (doanh va)) cac tap ((co soi) OR (cot soi)) viet nam ) OR ( chuong ((trinh chao) OR (trinh chat)) lanh ((dao cao) OR (tao cao)) cap do ((choi viet) OR (hoi viet)) nam ))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( cong trinh cham ((lanh va) or (doanh va)) cac tap ((co soi) or (cot soi)) viet nam ) or ( chuong ((trinh chao) or (trinh chat)) lanh ((dao cao) OR (tao cao)) cap do ((choi viet) or (hoi viet)) nam ))~".
• Adding a wildcard symbol may retrieve word variants: (( cong trinh cham ((lanh va) or (doanh va)) cac tap ((co soi) or (cot soi)) viet nam ) or ( chuong ((trinh chao) or (trinh chat)) lanh ((dao cao) OR (tao cao)) cap do ((choi viet) or (hoi viet)) nam ))*.