Perhaps you should try some spelling variations:
hieu quan » hieu qua, lieu quan, thien quan
nang cong » nang song, bang cong, hang cong
dang cong » dung cong
trang va » tran van, hang va
tan than » tan thanh, tan tran, ban than
than ban » thanh ban, toan ban, than man
ho hieu » ho chieu, hoi hieu, nho hieu
tang va » tang van, thang va, tang vat

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