1. Berkowitz, L., Macaulay, J.: Altruism and Helping Behavior: Social Psychological Studies of Some Antecedents and Consequences. Academic Press, New York (1970)
2. Buchanan, D., Huczynski, A.: Organisational Behaviour: An Introductory Text. Prentice Hall, London (1997)
3. Lecture Notes in Computer Science;M. Eberling,2009
4. Erdõs, P., Rényi, A.: On random graphs. Publicationes Mathematicae 6, 290–297 (1959)
5. Lecture Notes in Artificial Intelligence;D. Hales,2003