Perhaps you should try some spelling variations:
trinh xuong » trinh duong, trinh huong, trinh phuong
xuong quan » xuong quang, luong quan, cuong quan
hieu soat » hieu suat, hieu so, hieu hoa
kiem soat » kiem toan
hieu hoat » hieu hoa, thien hoat, hieu suat
hieu luat » hieu qua
quan van » luan van, quan va, quan luan

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: trinh xuong quan van ((((hieu soat) OR (kiem soat))) OR (((hieu hoat) OR (hieu luat))))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "trinh xuong quan van ((((hieu soat) or (kiem soat))) or (((hieu hoat) OR (hieu luat))))~".
• Adding a wildcard symbol may retrieve word variants: trinh xuong quan van ((((hieu soat) or (kiem soat))) or (((hieu hoat) OR (hieu luat))))*.