theorem
  rfs(r).n = 0 & n <= m implies scf(r).m = 0
proof
  assume
A1: rfs(r).n = 0 & n <= m;
  thus scf(r).m = [\rfs(r).m/] by Def4
    .= [\0/] by A1,Th27
    .= 0;
end;
