
theorem
  for Omega being set st Omega = {1,2,3,4} holds
    {1} c= Omega &
    {2} c= Omega &
    {3} c= Omega &
    {4} c= Omega &
    {1,2} c= Omega &
    {3,4} c= Omega &
    {} c= Omega &
    Omega c= Omega
proof
  let Omega be set;
  assume A0: Omega={1,2,3,4}; then
  1 in Omega & 2 in Omega & 3 in Omega & 4 in Omega by ENUMSET1:def 2;
  hence thesis by A0,Lemacik2,ZFMISC_1:31;
end;
