Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu qua, diep quang
trinh quan » tinh quang, trinh luat
nhung cong » dung cong, thong cong, hang cong
hieu quan » hieu qua, lieu quan, thien quan
cong tan » cong tac, cong san, cong thanh
tan phan » toan phan, than phan, van phan
phan cau » phan dau, phan cac, phan tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ho ((hieu quang) or (hieu quan)) - hanh ((trinh quan) OR (trinh han)) nhung cong tan phan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho ((hieu quang) OR (hieu quan)) - hanh ((trinh quan) OR (trinh han)) nhung cong tan phan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu quang) or (hieu quan)) - hanh ((trinh quan) OR (trinh han)) nhung cong tan phan cau".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu quang) or (hieu quan)) - hanh ((trinh quan) OR (trinh han)) nhung cong tan phan cau*.