theorem
  All(x,'not' H) is_proper_subformula_of Ex(x,H) & 'not' H
  is_proper_subformula_of Ex(x,H)
proof
  All(x,'not' H) is_immediate_constituent_of Ex(x,H);
  hence
A1: All(x,'not' H) is_proper_subformula_of Ex(x,H) by ZF_LANG:61;
  'not' H is_immediate_constituent_of All(x,'not' H);
  hence thesis by A1,Th40;
end;
