Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh trinh » canh tranh, hanh chinh
nhung cong » dung cong, thong cong, nhung don
hieu sang » chieu sang, hieu lang, nhieu tang
trinh cua » tinh cua, trinh luat, trinh quan
hang cong » dang cong, hang nong, bang cong
san toan » van toan, dan toan, 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 quang)) - hanh trinh cua ((nhung cong) OR (hang cong)) san toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu quang)) - hanh trinh cua ((nhung cong) OR (hang cong)) san toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sang) or (hieu quang)) - hanh trinh cua ((nhung cong) OR (hang cong)) san toan cau".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu quang)) - hanh trinh cua ((nhung cong) OR (hang cong)) san toan cau*.