Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh hang » thanh hang, hang hang, hanh han
hoc hieu » hoc thieu, hoc hien, doc hieu
cong dan » cong san, huong dan, cong dong
cong tan » cong tac, cong san, cong thanh
toan tai » toan tap, doanh tai, toan cao
toan ban » van ban

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

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