reserve G,G1,G2 for _Graph;
reserve e,x,y for set;
reserve v,v1,v2 for Vertex of G;
reserve W for Walk of G;

theorem
  v in G.reachableDFrom(v)
proof
  G.walkOf(v) is_Walk_from v,v by GLIB_001:13;
  hence thesis by Def6;
end;
