graph.dot

digraph causal
{
	a [label="1"]
	b [label="1"]
	c [label="1"]
	d [label="2"]
	e [label="2"]
	f [label="2"]
	g [label="3"]
	h [label="3"]
	i [label="3"]
	a -> b [type=1];
	a -> c
	b -> c [type=1];
	b -> a
	c -> b
	c -> a
	c -> d
	d -> e
	e -> f
	f -> g
	g -> h
	g -> i
	h -> i
	h -> g
	i -> h
	i -> g
	i -> a
}