“The Quadrilaterals′ Corner.” Charming Proofs: A Journey into Elegant Mathematics, by Claudi Alsina and Roger B. Nelsen, 1st ed., vol. 42, Mathematical Association of America, 2010, pp. 107–120, www.jstor.org/stable/10.4169/j.ctt6wpwnz.11. Accessed 24 June 2021.
Alsina, C., & Nelsen, R. (2010). The Quadrilaterals′ Corner. In Charming Proofs: A Journey into Elegant Mathematics (pp. 107-120). Mathematical Association of America. Retrieved June 24, 2021, from http://www.jstor.org/stable/10.4169/j.ctt6wpwnz.11
Alsina, Claudi, and Roger B. Nelsen. "The Quadrilaterals′ Corner." In Charming Proofs: A Journey into Elegant Mathematics, 107-20. Mathematical Association of America, 2010. Accessed June 24, 2021. http://www.jstor.org/stable/10.4169/j.ctt6wpwnz.11.
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