Perhaps you should try some spelling variations:
khong xuan » thong xuan, khong quan, khong xuong
tinh khong » tinh khang, tinh huong, benh khong
hieu suat » hieu luat, hieu qua
kien soat » kiem soat, bien soan, kien hoa
quan van » luan van, quan va, quan doan
van hieu » cao hieu
xuan van » luan van, xuan can, xuan tan
van kien » van tien, van hien, van chien
luan » lan

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh ((quan van) OR (quan luan)) van hieu suat ) or ( tinh khong xuan van kien soat ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh ((quan van) OR (quan luan)) van hieu suat ) OR ( tinh khong xuan van kien soat )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tinh ((quan van) OR (quan luan)) van hieu suat ) or ( tinh khong xuan van kien soat ))".
• Adding a wildcard symbol may retrieve word variants: (( tinh ((quan van) OR (quan luan)) van hieu suat ) or ( tinh khong xuan van kien soat ))*.