
theorem
  for G being _Graph st G.minDegree() = 0
  ex v being Vertex of G st v is isolated
proof
  let G be _Graph;
  assume G.minDegree() = 0;
  then consider v being Vertex of G such that
    A1: v.degree() = 0 and
    for w being Vertex of G holds v.degree() c= w.degree() by Th36;
  take v;
  thus thesis by A1, GLIB_000:157;
end;
