Bruneo, D., F. Longo, and A. Puliafito,  "Modeling energy-aware cloud federations with SRNs",  32nd International Conference on Application and Theory of Petri Nets and Concurrency (Petri Nets), vol. 7400 Lecture Notes in Computer Science, Newcastle upon Tyne, United Kingdom, 20-24 June 2011, Springer-Verlag, pp. 277-307, 2012.