Perhaps you should try some spelling variations:
quang hang » quang hoang, quang khang, quang thang
hieu suat » hieu luat, hieu qua
trinh han » trinh quan
dien toan » dien thanh, dien thoai, dien hoa
han tran » hoan tran, tan tran, ha tran
tran van » luan van
van dien » van tien, van hien, van kien
va hieu » van hieu, va dieu, va hien
tinh » dinh, minh, kinh

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 hang va hieu suat ) or ( trinh han tran van dien toan ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tinh quang hang va hieu suat ) OR ( trinh han tran van dien toan ))*.