reserve G for _Graph;

theorem
  for G being non-Dmulti _Graph holds G.size() c= card VertexAdjSymRel(G)
proof
  let G be non-Dmulti _Graph;
  card VertexDomRel(G) = card Class DEdgeAdjEqRel(G) by Th10;
  then G.size() = card Class DEdgeAdjEqRel(G) by Th12;
  hence G.size() c= card VertexAdjSymRel(G) by Th41;
end;
