Perhaps you should try some spelling variations:
trinh quan » tinh quang, trinh luat, trinh han
quan hang » quan hoang, quan lang, quan hanh
hieu soat » hieu suat, hieu hoat, hieu luat
dung nang » dun nang, dung dang, dung quang
nang van » dang van, tang van, lang van
van kien » van tien, van hien, van chien
kien hoa » dien hoa, tien hoa, kien ha
va hieu » van hieu, va dieu, va hien

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( trinh quan hang va hieu soat ) or ( tin dung nang van kien hoa ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( trinh quan hang va hieu soat ) OR ( tin dung nang van kien hoa )).
• Adding a wildcard symbol may retrieve word variants: (( trinh quan hang va hieu soat ) or ( tin dung nang van kien hoa ))*.