El Farissi, Abdallah, and Benharrat Bela¨ıdi. “Oscillation and Fixed Points of Derivatives of Solutions of Some Linear Differential Equations”. MATEMATIKA: Malaysian Journal of Industrial and Applied Mathematics 30 (December 1, 2014): 159–168. Accessed September 18, 2021. https://matematika.utm.my/index.php/matematika/article/view/707.