A generalized preferential attachment model for business firms growth rates - II. Mathematical treatmentS. V. Buldyrev, F. Pammolli, M. Riccaboni, K. Yamasaki, D.-F. Fu, K. Matia and H. E. StanleyEur. Phys. J. B, 57 2 (2007) 131-138DOI: https://doi.org/10.1140/epjb/e2007-00165-8