reserve Y for non empty set;
reserve Y for non empty set;
reserve Y for non empty set;
reserve Y for non empty set,
  a,b,c,d,e,f,g for Function of Y,BOOLEAN;
reserve Y for non empty set;

theorem
  for a,b,c being Function of Y,BOOLEAN holds (a 'or' 'not' b) '&'
  (b 'or' 'not' c) '&' (c 'or' 'not' a)= (b 'or' 'not' a) '&' (c 'or' 'not' b)
  '&' (a 'or' 'not' c)
proof
  let a,b,c be Function of Y,BOOLEAN;
  (a 'or' 'not' b) '&' (b 'or' 'not' c) '&' (c 'or' 'not' a) '<' (b 'or'
  'not' a) '&' (c 'or' 'not' b) '&' (a 'or' 'not' c) & (b 'or' 'not' a) '&' (c
  'or' 'not' b) '&' (a 'or' 'not' c) '<' (a 'or' 'not' b) '&' (b 'or' 'not' c)
  '&' (c 'or' 'not' a) by Lm2;
  hence thesis by BVFUNC_1:15;
end;
