Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hieu lang » chieu sang, nhieu tang, hieu van
hanh sinh » hanh tinh, hanh dinh, hanh chinh
hinh sinh » tinh sinh, hinh dinh, hinh kinh
dung cong » dung trong
trinh van » trinh han, trinh quan, trinh toan
cua dung » cua dang, cua dong, qua dung
van dau » van dao, phan dau

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 lang) or (hieu quang)) - ((hanh sinh) OR (hinh sinh)) cua dung cong trinh van dau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ho ((hieu lang) OR (hieu quang)) - ((hanh sinh) OR (hinh sinh)) cua dung cong trinh van dau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu lang) or (hieu quang)) - ((hanh sinh) OR (hinh sinh)) cua dung cong trinh van dau".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) or (hieu quang)) - ((hanh sinh) OR (hinh sinh)) cua dung cong trinh van dau*.