Perhaps you should try some spelling variations:
hanh trang » thanh trung, hanh trinh, minh trang
hieu quan » hieu qua, lieu quan, thien quan
hang cong » dang cong, hang nong, bang cong
vang toan » van toan, quang toan, vang trang
dang toan » dang tran, dan toan, dung toan
hoc hieu » hoc thieu, hoc hien, doc hieu
va hang » van hang, va nang, va 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) or (canh tranh)) va hang cong ((vang toan) OR (dang toan)) ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu quan - ((hanh trang) OR (canh tranh)) va hang cong ((vang toan) OR (dang toan)) ban.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu quan - ((hanh trang) or (canh tranh)) va hang cong ((vang toan) OR (dang toan)) ban".
• Adding a wildcard symbol may retrieve word variants: hoc hieu quan - ((hanh trang) or (canh tranh)) va hang cong ((vang toan) OR (dang toan)) ban*.