reserve D for non empty set,
  i,j,k for Nat,
  n,m for Nat,
  r for Real,
  e for real-valued FinSequence;

theorem Th54:
  for M being non empty-yielding Matrix of D holds 1<=len M & 1<= width M
proof
  let M be non empty-yielding Matrix of D;
  ( not len M=0)& not width M=0 by MATRIX_0:def 10;
  hence thesis by NAT_1:14;
end;
