Perhaps you should try some spelling variations:
hieu quan » hieu qua, lieu quan, thien quan
cong dan » cong san, huong dan, cong dong
cong tan » cong tac, cong san, cong thanh
toan cao » toan tap
toan ban » van ban
ho hieu » ho chieu, hoi hieu, nho hieu
kinh va » kinh van, tinh va, sinh va

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: ho hieu quan - than kinh va nhung ((cong dan) OR (cong tan)) ((toan cao) OR (toan ban))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho hieu quan - than kinh va nhung ((cong dan) OR (cong tan)) ((toan cao) or (toan ban))~".
• Adding a wildcard symbol may retrieve word variants: ho hieu quan - than kinh va nhung ((cong dan) OR (cong tan)) ((toan cao) or (toan ban))*.