References for Kenneth Appel
- R Wilson, Four Colors Suffice: How the Map Problem Was Solved (Princeton University Press, Princeton, 2002).
- K I Appel, Roger C Lyndon: a biographical and personal note, in K I Appel, J G Ratcliffe and P E Schupp (eds.), Contributions to group theory, Contemporary Mathematics 33 (Prividence, 1984), 1-10.
- K I Appel, The Use of the Computer in the Proof of the Four Color Theorem, Proc. Amer. Philos. Soc. 128 (1) (1984), 35-39.
- K I Appel and W Haken, The Nature of Proof: Limits and Opportunities, The Two-Year College Mathematics Journal 12 (2) (1981), 118-119.
- K I Appel and W Haken, The Four Color Proof Suffices, The Mathematical Intelligencer 8 (1) (1986), 10-20.
- Kenneth Appel, mathematician of maps, died on April 19th, aged 80, The Economist (4 May 2013).
- Kenneth Appel, 80; first to use a computer to prove a major math theorem, The Boston Globe (30 April 2013).
- D Brooks, Proving the four-color theorem expanded math's frontiers, University of New Hampshire Magazine Online (Spring 2002).
- M Kingston, Famed mathematician Ken Appel recalled fondly, Fosters.com.
- Obituary: Kenneth I Appel (October 8, 1932 - April 19, 2013), Tasker Funeral Service.
- D Overbye, Kenneth I Appel, Mathematician Who Harnessed Computer Power, Dies at 80, The New York Times (28 April 2013).
- R Thomas, An update on the Four Color Theorem, Notices Amer. Math. Soc. 45 (7) (1998), 848-859.
- B Toft, Review: Four Colors Suffice: How the Map Problem Was Solved, by Robin Wilson, Notices Amer. Math. Soc. 51 (2) (2004), 205-207.
- A Ward, Kenneth Appel Dies: Mathematician Ushered Computer Into Everyday Use, Newsmax (30 April 2013).
- M Weil, Kenneth Appel, mathematician who solved four-color map problem, dies at 80, The Washington Post (30 April 2013).