Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh tranh » canh tranh, hanh trinh, hanh trang
cua truong » cua trung, xuan truong, cac truong
cua trong » cua trung, qua trong, ca trong
hoc hieu » hoc thieu, hoc hien, doc hieu
van toan » van tuan, van tan, van thanh
dan toan » dan than, manh toan, xuan toan

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 quang - hanh tranh ((cua trong) OR (cua truong)) cong ((van toan) or (dan toan)) tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu quang - hanh tranh ((cua trong) OR (cua truong)) cong ((van toan) OR (dan toan)) tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu quang - hanh tranh ((cua trong) OR (cua truong)) cong ((van toan) or (dan toan)) tap".
• Adding a wildcard symbol may retrieve word variants: hoc hieu quang - hanh tranh ((cua trong) OR (cua truong)) cong ((van toan) or (dan toan)) tap*.