digraph constr_doubl {
center=true;
me3 -> me1;
me3 -> me2;
me6 -> me4;
me6 -> me5;
me7 -> me3;
me7 -> me6;
e1 [ shape= box, label= "E1" ];
e2 [ shape= box, label= "E2" ];
e3 [ shape= box, label= "E3" ];
e4 [ shape= box, label= "E4" ];
e5 [ shape= box, label= "E5" ];
e6 [ shape= box, label= "E6" ];
e7 [ shape= box, label= "E7" ];
e8 [ shape= box, label= "E8" ];
{ rank= same; e1; e2; e3; e4; e5; e6; e7; e8 }
e1 -> e2 [ style= "invis"] ;
e2 -> e3 [ style= "invis"] ;
e3 -> e4 [ style= "invis"] ;
e4 -> e5 [ style= "invis"] ;
e5 -> e6 [ style= "invis"] ;
e6 -> e7 [ style= "invis"] ;
e7 -> e8 [ style= "invis"] ;
me1 [ shape= ellipse, label= "ME1" ];
me2 [ shape= ellipse, label= "ME2" ];
me3 [ shape= ellipse, label= "ME3" ];
me4 [ shape= ellipse, label= "ME4" ];
me5 [ shape= ellipse, label= "ME5" ];
me6 [ shape= ellipse, label= "ME6" ];
me7 [ shape= ellipse, label= "ME7" ];
me1 -> e1 ;
me1 -> e2 ;
me2 -> e3 ;
me2 -> e4 ;
me4 -> e5 ;
me4 -> e6 ;
me5 -> e7 ;
me5 -> e8 ;
}