Perhaps you should try some spelling variations:
thien hieu » thien nhien, thien chien, thien hue
thong cong » trong cong, tong cong, thong thong
hieu lang » chieu sang, hieu quang, nhieu tang
manh toan » thanh toan, anh tuan, tinh toan
trang va » tran van, hang va
quan van » luan van, quan va, quan luan
dan toan » van toan, dan than, xuan toan

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

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