Appel, K. and Haken, W. "Every Planar Map is Four-Colorable, II: Reducibility." Illinois J. Math.21, 491-567, 1977.Appel, K. and Haken, W. "The Solution of the Four-Color Map Problem." Sci. Amer.237, 108-121, 1977.Appel, K. and Haken, W. "The Four Color Proof Suffices." Math. Intell.8, 10-20 and 58, 1986.Appel, K. and Haken, W. Every Planar Map is Four-Colorable. Providence, RI: Amer. Math. Soc., 1989.Appel, K.; Haken, W.; and Koch, J. "Every Planar Map is Four Colorable. I: Discharging." Illinois J. Math.21, 429-490, 1977.Barnette, D. Map Coloring, Polyhedra, and the Four-Color Problem. Providence, RI: Math. Assoc. Amer., 1983.Birkhoff, G. D. "The Reducibility of Maps." Amer. Math. J.35, 114-128, 1913.Chartrand, G. "The Four Color Problem." §9.3 in Introductory Graph Theory. New York: Dover, pp. 209-215, 1985.Coxeter, H. S. M. "The Four-Color Map Problem, 1840-1890." Math. Teach.52, 283-289, 1959.Devlin, K. "Devlin's Angle: Last Doubts Removed About the Proof of the Four Color Theorem." Jan. 2005.Errera, A. Du colorage de cartes et de quelques questions d'analysis situs. Ph.D. thesis. Paris: Gauthier-Villars, 1921.Franklin, P. "Note on the Four Color Problem." J. Math. Phys.16, 172-184, 1937-1938.Franklin, P. The Four-Color Problem. New York: Scripta Mathematica, Yeshiva College, 1941.Gardner, M. "Mathematical Games: The Celebrated Four-Color Map Problem of Topology." Sci. Amer.203, 218-222, Sep. 1960.Gardner, M. "Mathematical Games: Martin Gardner's New Mathematical Diversions from Scientific American." Sci. Amer.232, 127-132, Apr. 1975.Gardner, M. "Mathematical Games: Six Sensational Discoveries that Somehow or Another have Escaped Public Attention." Sci. Amer.232, 127-132, Apr. 1975.Gardner, M. "Mathematical Games: On Tessellating the Plane with Convex Polygons." Sci. Amer.232, 112-117, Jul. 1975.Gardner, M. The Last Recreations: Hydras, Eggs, and Other Mathematical Mystifications. New York: Springer-Verlag, p. 86, 1997.Gethner, E. and Springer, W. M. II. "How False Is Kempe's Proof of the Four-Color Theorem?" Congr. Numer.164, 159-175, 2003.Harary, F. "The Four Color Conjecture." Graph Theory. Reading, MA: Addison-Wesley, p. 5, 1994.Heawood, P. J. "Map Colour Theorems." Quart. J. Math.24, 332-338, 1890.Heawood, P. J. "On the Four-Color Map Theorem." Quart. J. Pure Math.29, 270-285, 1898.Hutchinson, J. P. and Wagon, S. "Kempe Revisited." Amer. Math. Monthly105, 170-174, 1998.Kempe, A. B. "On the Geographical Problem of Four-Colors." Amer. J. Math.2, 193-200, 1879.Kittell, I. "A Group of Operations on a Partially Colored Map." Bull. Amer. Math. Soc.41, 407-413, 1935.Knight, W. "Computer Generates Verifiable Mathematics Proof." New Scientist Breaking News. Apr. 19, 2005.Kraitchik, M. §8.4.2 in Mathematical Recreations. New York: W. W. Norton, p. 211, 1942.May, K. O. "The Origin of the Four-Color Conjecture." Isis56, 346-348, 1965.Morgenstern, C. and Shapiro, H. "Heuristics for Rapidly 4-Coloring Large Planar Graphs." Algorithmica6, 869-891, 1991.Ore, Ø. The Four-Color Problem. New York: Academic Press, 1967.Ore, Ø. and Stemple, G. J. "Numerical Methods in the Four Color Problem." Recent Progress in Combinatorics (Ed. W. T. Tutte). New York: Academic Press, 1969.Pappas, T. "The Four-Color Map Problem: Topology Turns the Tables on Map Coloring." The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, pp. 152-153, 1989.Ringel, G. and Youngs, J. W. T. "Solution of the Heawood Map-Coloring Problem." Proc. Nat. Acad. Sci. USA60, 438-445, 1968.Robertson, N.; Sanders, D. P.; Seymour, P. D.; and Thomas, R. "A New Proof of the Four Colour Theorem." Electron. Res. Announc. Amer. Math. Soc.2, 17-25, 1996.Robertson, N.; Sanders, D. P.; and Thomas, R. "The Four-Color Theorem." http://www.math.gatech.edu/~thomas/FC/fourcolor.html.Saaty, T. L. and Kainen, P. C. The Four-Color Problem: Assaults and Conquest. New York: Dover, 1986.Skiena, S. Implementing Discrete Mathematics: Combinatorics and Graph Theory with Mathematica. Reading, MA: Addison-Wesley, p. 210, 1990.Steinhaus, H. Mathematical Snapshots, 3rd ed. New York: Dover, pp. 274-275, 1999.Tait, P. G. "Note on a Theorem in Geometry of Position." Trans. Roy. Soc. Edinburgh29, 657-660, 1880.Thomas, R. "An Update on the Four-Color Theorem." Not. Amer. Math. Soc.45, 858-857, 1998.Weisstein, E. W. "Books about Four-Color Problem." http://www.ericweisstein.com/encyclopedias/books/Four-ColorProblem.html.Wells, D. The Penguin Dictionary of Curious and Interesting Numbers. Middlesex, England: Penguin Books, p. 57, 1986.Wells, D. The Penguin Dictionary of Curious and Interesting Geometry. London: Penguin, pp. 81-82, 1991.Wilson, R. Four Colors Suffice : How the Map Problem Was Solved. Princeton, NJ: Princeton University Press, 2004.
，希伍德猜想提供的上限也給出了必要的顏色數，但克萊因瓶（希伍德公式給出 7，但正確的界限是 6）除外。
的情況，並且這個數字很容易減少到五種，但是將顏色數量一直減少到四種被證明非常困難。阿佩爾和哈肯（1977 年）最終獲得了這個結果，他們構建了一個計算機輔助證明，證明四種顏色就足夠了。然而，由於部分證明包括計算機對許多離散情況的詳盡分析，一些數學家不接受它。但是，尚未發現任何缺陷，因此該證明看起來有效。羅伯遜等人。（1996 年；托馬斯 1998 年）構建了一個更短、獨立的證明。