Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh trang » thanh trung, hanh trinh, minh trang
hieu lang » chieu sang, nhieu tang, hieu van
thong dan » thong van, tuong dan, thong den
va thong » va thuong, va phuong, he thong
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan tap

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