Klein-Gordon equation from the path integral formalism D. Felea, C. Beşliu, I.S. Zgură, R. Mărginean, Al. Jipa and R.I. Nanciu Eur. Phys. J. C, 20 4 (2001) 713-716 Published online: 15 May 2001 DOI: 10.1007/s100520100693