Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hieu lang » chieu sang, hieu quang, nhieu tang
trang cua » tang cua, trung cua, thang cua
tranh cua » doanh cua, manh cua
hoc hieu » hoc thieu, hoc hien, doc hieu
san toan » van toan, manh toan, xuan toan
dan toan » van toan, dan than, manh toan

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc hieu lang - hanh ((trang cua) or (tranh cua)) nhung cong ((san toan) OR (dan toan)) cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu lang - hanh ((trang cua) OR (tranh cua)) nhung cong ((san toan) OR (dan toan)) cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu lang - hanh ((trang cua) or (tranh cua)) nhung cong ((san toan) OR (dan toan)) cau".
• Adding a wildcard symbol may retrieve word variants: hoc hieu lang - hanh ((trang cua) or (tranh cua)) nhung cong ((san toan) OR (dan toan)) cau*.