Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
thong cong » trong cong, tong cong, thong thong
hieu lang » chieu sang, nhieu tang, hieu van
cong manh » cong danh, duong manh, cong thanh
manh toan » thanh toan, anh tuan, tinh toan
trang va » tran van, hang va
toan cau » toan cao, toan ban, toan tap
luan » quan, lan

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