Perhaps you should try some spelling variations:
hanh trang » thanh trung, canh tranh, hanh trinh
hieu quan » hieu qua, lieu quan, thien quan
cong dung » cuong dung, cong dong, cong luong
thanh ban » thanh van, thanh bac, thanh bai
hoc hieu » hoc thieu, hoc hien, doc hieu
va hang » van hang, va nang, va hanh
va lang » va nang, hoa lang

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: hoc hieu quan - hanh trang ((va hang) or (va lang)) cong dung ((thanh ban) OR (thanh san))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu quan - hanh trang ((va hang) OR (va lang)) cong dung ((thanh ban) OR (thanh san)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu quan - hanh trang ((va hang) or (va lang)) cong dung ((thanh ban) OR (thanh san))".
• Adding a wildcard symbol may retrieve word variants: hoc hieu quan - hanh trang ((va hang) or (va lang)) cong dung ((thanh ban) OR (thanh san))*.