theorem Th49:
  k + 1 > d implies for C being Chain of (k + 1),G holds del C = 0_(k,G)
proof
  assume
A1: k + 1 > d;
  let C be Chain of (k + 1),G;
  for A being object holds not A in del C by A1,Th48;
  hence thesis by XBOOLE_0:def 1;
end;
