Klein-Gordon equation from the path integral formalism D. Felea, C. Beşliu, I.S. Zgură, R. Mărginean, Al. Jipa and R.I. NanciuEur. Phys. J. C, 20 4 (2001) 713-716DOI: https://doi.org/epjc/v20/p713(epjc0693)