This image was made using tools called tred and dot, both part of the graphviz package of tools for manipulating and visualizing graphs. First, the dot file Tred-Gprime.dot was created using tred and the dot file for Tred-G.png by issuing the following command:

tred < Tred-G.dot > Tred-Gprime.dot

The result was the following dot file:

digraph g {
  a -> b;
  a -> c;
  b -> d;
  c -> d;
  d -> e;
}

The image itself was then created using the following command:

dot -Tsvg Tred-Gprime.dot -o Tred-Gprime.svg