reserve x,y,z for object,
  i,j,n,m for Nat,
  D for non empty set,
  s,t for FinSequence,
  a,a1,a2,b1,b2,d for Element of D,
  p, p1,p2,q,r for FinSequence of D;

theorem Th13:
  {} is Matrix of 0,m,D
proof
  reconsider M =<*>(D*) as FinSequence of D*;
  reconsider M as Matrix of D by Th5;
  M is (0,m)-size;
  hence thesis;
end;
