Perhaps you should try some spelling variations:
dung quang » dang quang, dung quan, luong quang
thien hoat » thien thuat, tien hoa
trien hoat » tien hoa
hieu suat » hieu luat, hieu qua
quang ban » quang binh, quang tuan, quang tran
quang va » quang van, quan va, quang ma
va hieu » van hieu, va dieu, va hien
ban dan » ban hang, ban hanh, ban quan

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tin dung quang va hieu suat ) or ( tinh quang ban dan ((thien hoat) OR (trien hoat)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tin dung quang va hieu suat ) OR ( tinh quang ban dan ((thien hoat) OR (trien hoat)) )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tin dung quang va hieu suat ) or ( tinh quang ban dan ((thien hoat) OR (trien hoat)) ))".
• Adding a wildcard symbol may retrieve word variants: (( tin dung quang va hieu suat ) or ( tinh quang ban dan ((thien hoat) OR (trien hoat)) ))*.