digraph g {
"context" -> "simple Feynman diagram"
"e1" -> "gamma 1" [label="electron",arrowhead=normal]
"gamma 1" -> "e2" [label="electron",arrowhead=normal]
"gamma 1" -> "gamma 2" [label="photon",arrowhead=normal]
"e3" -> "gamma 2" [label="electron",arrowhead=normal]
"gamma 2" -> "e4" [label="electron",arrowhead=normal]
}