reserve x, y, z, v for set,
  n, m, k for Nat;
reserve G, G1, G2, G3 for Graph;
reserve x, y for Element of (the carrier of G);

theorem Th29:
  for G being strict Graph holds G in bool G
proof
  let G be strict Graph;
 G is Subgraph of G by Def24;
  hence thesis by Def25;
end;
