Perhaps you should try some spelling variations:
thong cong » trong cong, tong cong, thong thong
hieu lang » chieu sang, hieu quang, nhieu tang
trinh cua » trinh luat, trinh quan, trinh luan
nho hieu » nha hieu, nho sieu, nhu hieu
tinh cua » sinh cua, tinh chat, tranh cua
dan toan » van toan, manh toan, xuan toan
dan than » dan chan, ban than, van than

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

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