Perhaps you should try some spelling variations:
thong cong » trong cong, tong cong, thong thong
hieu lang » chieu sang, hieu quang, nhieu tang
hoang van » hang va
trinh han » trinh quan
dang van » hang va
he hieu » he nhieu, he dieu, de hieu
han cau » hang cau, phan cau, van cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: he hieu lang - hanh ((hoang van) or (dang van)) thong cong trinh han cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: he hieu lang - hanh ((hoang van) OR (dang van)) thong cong trinh han cau*.