Perhaps you should try some spelling variations:
cong thuong » hang thuong
thuong kinh » truong kinh, thuong binh, thuong tinh
chieu sang » chieu sach, chieu xanh, nhieu tang
hieu lang » hieu quang, nhieu tang, hieu van
quang va » quang van, quan va, quang ma
kinh van » dinh van, vinh van, binh van
va cong » tai cong, cua cong

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((chieu sang) or (hieu lang)) - tinh quang va cong thuong kinh van ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((chieu sang) OR (hieu lang)) - tinh quang va cong thuong kinh van ban*.