Gauge transformations are canonical transformations, redux
  In this short note we return to the old paper by Tai L. Chow (Eur. J. Phys. 18 (1997), 467-468) and correct its erroneous final part. We also note that the main result of that paper, that gauge transformations of mechanics are canonical transformations, was known much earlier. 
Z.K. Silagadze
physics.class-ph math-ph math.MP