Perhaps you should try some spelling variations:
hieu suat » hieu luat, hieu qua
tinh quan » tinh quang, trinh quan, tin quan
dung sai » dung tai, dung dat, dung ha
van hieu » cao hieu
quan lan » quan luan, quan lang, quan van
van dien » van tien, van hien, van kien
lan van » luan van, lang van, tan van
hoa » khoa

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

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