reserve G, G1, G2 for _Graph, H for Subgraph of G;

theorem Th160:
  field SubtreeRel(G) = G.allTrees()
proof
  G.allTrees() c= G.allSG();
  then G.allTrees() c= field SubgraphRel(G) by Th40;
  hence thesis by ORDERS_1:71;
end;
