Perhaps you should try some spelling variations:
trinh xuong » trinh duong, trinh phuong, trinh truong
trinh huong » trinh phuong, tinh huong, trinh duong
hieu soat » hieu suat, kiem soat, hieu so
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.

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