
theorem Th28:
  for G being _Graph, W being Walk of G st len W = 3 or W.length() = 1
  ex e being object st e Joins W.first(),W.last(),G &
    W = G.walkOf(W.first(),e,W.last())
proof
  let G be _Graph, W be Walk of G;
  assume len W = 3 or W.length() = 1;
  then per cases;
  suppose len W = 3;
    hence thesis by Lm2;
  end;
  suppose W.length() = 1;
    then len W = 2*1 + 1 by GLIB_001:112;
    hence thesis by Lm2;
  end;
end;
