Appel, K. I., & Haken, W. (1989). Every planar map is four colorable. American Mathematical Society.
Citación estilo ChicagoAppel, Kenneth I., and Wolfgang Haken. Every Planar Map Is Four Colorable. Providence: American Mathematical Society, 1989.
Cita MLAAppel, Kenneth I., and Wolfgang Haken. Every Planar Map Is Four Colorable. American Mathematical Society, 1989.
Warning: These citations may not always be 100% accurate.