Katsala, R. A., and M. M. Pahirya. “Properties of Reciprocal Derivatives”. Ukrains’kyi Matematychnyi Zhurnal 62, no. 5 (May 25, 2010): 708–713. Accessed May 4, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/2902.