Pankaj K. Agarwal, Rinat Ben Avraham, Micha Sharir. The 2-center problem in three dimensions. In Jack Snoeyink, Mark de Berg, Joseph S. B. Mitchell, Günter Rote, Monique Teillaud, editors, Proceedings of the 26th ACM Symposium on Computational Geometry, Snowbird, Utah, USA, June 13-16, 2010. pages 87-96, ACM, 2010. [doi]
Abstract is missing.