Perhaps you should try some spelling variations:
quang quan » quang tuan, quang uan, quan quan
hieu suat » hieu luat, hieu qua
khoa bien » hoa bien, khoa tieng, khoa dieu
quan bao » quang bao, quan ao, luan bao
bao hieu » bao nhieu, cao hieu, bao hiem
thi hanh » thi thanh
hanh da » hanh dao, hanh dua, hanh va
bien so » bien doi
tinh » trinh, dinh, minh

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tinh quang quan bao hieu suat ) or ( thi hanh da khoa bien so ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh quang quan bao hieu suat ) OR ( thi hanh da khoa bien so ))*.