
theorem
  for G being _Graph, E1, E2 being RepDEdgeSelection of G
  holds card E1 = card E2
proof
  let G be _Graph, E1, E2 be RepDEdgeSelection of G;
  consider f being one-to-one Function such that
    A1: dom f = E1 & rng f = E2 and
    for e,v,w being object st e in E1 holds e DJoins v,w,G iff f.e DJoins v,w,G
    by Th87;
  thus thesis by A1, WELLORD2:def 4, CARD_1:5;
end;
