Two-time correlation functions: stochastic and conventional quantum mechanics L. Feligioni, O. Panella, Y. N. Srivastava and A. Widom Eur. Phys. J. B, 48 2 (2005) 233-242 Published online: 16 December 2005 DOI: 10.1140/epjb/e2005-00399-4