reserve A,B,C,D,p,q,r for Element of LTLB_WFF,
        F,G,X for Subset of LTLB_WFF,
        M for LTLModel,
        i,j,n for Element of NAT,
        f,f1,f2,g for FinSequence of LTLB_WFF;

theorem
  ex F,A st F |= A & not F |=0 A
proof
  {prop 0} |= 'X' prop 0 & not {prop 0} |=0 'X' prop 0 by th262ac1;
  hence thesis;
end;
