digraph d
{
	fontname = Helvetica
	fontsize = 10
	label = "Fig. 2"
	rankdir = "LR"
	node [fontname = "Helvetica-Bold", fontsize = 12]

	subgraph cluster_Roots
	{
		fontname = "Helvetica-Bold"
		label = "Roots"
		fontsize = 15

		style = filled
		fillcolor = grey
		Globals [style = filled, fillcolor = white]
		Stack [style = filled, fillcolor = white]
	}
	
	a
	b
	c [style = filled, fillcolor = salmon]
	d [style = filled, fillcolor = salmon]
	e [style = filled, fillcolor = salmon]

	subgraph s
	{
		rank = same
		a
		c

		a -> c [style = invis]
	}

	Globals -> a -> b
	c -> d
	c -> e
}