1. Bajaj, C.: The algebraic degree of geometric optimization problems. Discr. Comput. Geom. 3, 177–191 (1988)
2. Courant, R., Robbins, H.: What is Mathematics? Oxford University Press, London (1941)
3. Drezner, Z., Hamacher, H.W. (eds.): Facility Location: Applications and Theory. Springer, Heidelberg (2004)
4. Eiselt, H.A., Marianov, V. (eds.): Foundations of Location Analysis. Springer, Heidelberg (2011)
5. Fermat–Torricelli problem. Encyclopedia of Mathematics (2012),
http://www.encyclopediaofmath.org/index.php?title=Fermat-Torricelli_problem&oldid=22419