Perhaps you should try some spelling variations:
hanh trang » thanh trung, canh tranh, hanh trinh
phuong dan » phuong danh, phuong doan, huong dan
hieu sang » chieu sang, hieu quang, nhieu tang
hieu lang » chieu sang, hieu quang, nhieu tang
va truong » van truong, xa truong, va tuong
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: doc ((hieu sang) OR (hieu lang)) - hanh trang ((va truong) or (va thuong)) phuong dan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu lang)) - hanh trang ((va truong) OR (va thuong)) phuong dan toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sang) OR (hieu lang)) - hanh trang ((va truong) or (va thuong)) phuong dan toan cau".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) OR (hieu lang)) - hanh trang ((va truong) or (va thuong)) phuong dan toan cau*.