Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu qua, diep quang
thong cong » trong cong, tong cong, thong thong
hieu quan » hieu qua, lieu quan, thien quan
tranh va » tranh van, trang va, thanh va
trinh va » trinh van, trinh vat, trinh ve
cong tan » cong tac, cong san, cong thanh
tan than » tan thanh, tan tran, ban than
than cap » khan cap, thanh lap, thanh cac

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

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