Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
hieu quang » thieu quang, hieu quan, hieu qua
dung duong » dong duong, dung dung, dung luong
hieu lang » chieu sang, nhieu tang, hieu van
dung dong » dung cong, vung dong, dung trong
trinh va » trinh van, trinh vat, trinh ve
tuan cau » toan cau, quan cau, tuan cu

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 quang) or (hieu lang)) - hanh trinh va ((dung duong) OR (dung dong)) anh tuan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu quang) OR (hieu lang)) - hanh trinh va ((dung duong) OR (dung dong)) anh tuan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu quang) or (hieu lang)) - hanh trinh va ((dung duong) OR (dung dong)) anh tuan cau".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu quang) or (hieu lang)) - hanh trinh va ((dung duong) OR (dung dong)) anh tuan cau*.