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 th261b:
  M |= A iff M |=0 'G' A
proof
  hereby assume M |= A;then
    for i holds (SAT M).[0+i,A]=1;
    hence M |=0 'G' A by LTLAXIO1:10;
  end;
  assume Z2: M |=0 'G' A;
  now
    let i;
    (SAT M).[0+i,A]=1 by LTLAXIO1:10,Z2;
    hence (SAT M).[i,A]=1;
  end;
  hence M |= A;
end;
