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MR1985159 (2004c:91079) Grossman, Jerrold W. The evolution of the mathematical research collaboration graph. Proceedings of the Thirty-third Southeastern International Conference on Combinatorics, Graph Theory and Computing (Boca Raton, FL, 2002). Congr. Numer. 158 (2002), 201--212. (Reviewer: Sandra L. Arlinghaus) 91D30 (01A80 05C80 05C90)