Chapter 2

www.tsp.gatech.edu

en.wikipedia.org/wiki/Minimum_cost_spanning_tree

http://www-gap.dcs.st-and.ac.uk/~history/Biographies/Hamilton.html

http://www.ams.org/samplings/feature-column/fcarc-tsp

http://www.ams.org/samplings/feature-column/fcarc-trees