Sommerville, D. M. Y. (1905). «Semi-regular networks of the plane in absolute geometry». Transactions of the Royal Society of Edinburgh. 41: 725-747. doi:10.1017/s0080456800035560
Grünbaum, Branko (2009). «An enduring error»(PDF). Elemente der Mathematik. 64 (3). pp. 89–101. doi:10.4171/EM/120 Reimpresso em Pitici, Mircea (2011). The Best Writing on Mathematics 2010. [S.l.]: Princeton University Press. pp. 18–31.
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Grünbaum, Branko (2009). «An enduring error»(PDF). Elemente der Mathematik. 64 (3). pp. 89–101. doi:10.4171/EM/120 Reimpresso em Pitici, Mircea (2011). The Best Writing on Mathematics 2010. [S.l.]: Princeton University Press. pp. 18–31.