Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
hieu cach » hieu cac, chieu sach, hieu ca
hoc hieu » hoc thieu, hoc hien, doc hieu
tranh va » tranh van, trinh va, thanh va
trang va » tran van, hang va
cong san » cong tac
toan cao » toan ban, toan tap

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 cach - canh ((tranh va) OR (trang va)) nhung cong san ((van ban) OR (toan cao))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu cach - canh ((tranh va) OR (trang va)) nhung cong san ((van ban) or (toan cao))~".
• Adding a wildcard symbol may retrieve word variants: hoc hieu cach - canh ((tranh va) OR (trang va)) nhung cong san ((van ban) or (toan cao))*.