A universal power law and proportionate change process characterize the evolution of metabolic networksS. Singh, A. Samal, V. Giri, S. Krishna, N. Raghuram and S. JainEur. Phys. J. B, 57 1 (2007) 75-80DOI: https://doi.org/10.1140/epjb/e2007-00145-0