reserve k,m,n for Element of NAT,
  i, j for Nat,
  a, b, c for object,
  X, Y, Z for set,
  D, D1, D2 for non empty set;
reserve p, q, r, s for FinSequence;

theorem Th1:
  'not' <> '&' & 'not' <> '=' & '&' <> '='
proof
  A1: 'not'.1 = 1;
  '&'.1 = 2;
  hence thesis by A1, FINSEQ_1:def 8;
end;
