reserve G for _Graph;

theorem
  card VertexDomRel(G) c= G.size()
proof
  set E = the RepDEdgeSelection of G;
  card E c= card the_Edges_of G by CARD_1:11;
  then card E c= G.size() by GLIB_000:def 25;
  then card Class DEdgeAdjEqRel(G) c= G.size() by GLIBPRE0:69;
  hence thesis by Th10;
end;
