digraph aef{
  /* HORIZONTAL */ rankdir=LR;
  /* NAME */ node [shape=plaintext, fontname=comic, fontsize=18, fontcolor=blue];
  A1;
  node [shape=circle, fontname=Georgia, fontsize=14, fontcolor=black];
  node [peripheries=2];
  "3"; "2";
  node [peripheries=1];
  A1 -> "1" [color=blue];
  "1" -> "1" [label="a"];
  "1" -> "2" [label="b"];
  "2" -> "2" [label="b"];
  "2" -> "1" [label="d"];
  "1" -> "3" [label="c"];
  }