digraph d
{
	fontname = Helvetica
	fontsize = 10
	label = "Fig. 3"
	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

	Stack -> a
	a -> b
	a -> c
	Globals -> a [style = dashed, color = cornflowerblue]
}