Agent-based simulation model to improve managerial capabilities, in a complexity perspective – review of M. J. North and C. M. Macal, Managing Business Complexity: Discovering Strategic Solutions with Agent-based Modeling and Simulation. Oxford University Press, Oxford and New York, 2007, 313 pp; M. Villani (ed.): Educating Managers in Complexity. Aracne, Roma, 2006, 364 pp.