Fritsch, R., & Fritsch, G. (1998). The four color theorem: History, topological foundations, and idea of proof. Springer.
استشهاد بنمط شيكاغوFritsch, Rudolf, و Gerda Fritsch. The Four Color Theorem: History, Topological Foundations, and Idea of Proof. New York: Springer, 1998.
MLA استشهادFritsch, Rudolf, و Gerda Fritsch. The Four Color Theorem: History, Topological Foundations, and Idea of Proof. Springer, 1998.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.