Qocayeva , Nubar, and Mətin Həsənov. “Derivatives and Differentials of Multivariable Functions: A Theoretical and Applied Analysis ”. Luminis Applied Science and Engineering 3, no. 2 (April 14, 2026): 13–21. Accessed April 30, 2026. https://egarp.lt/index.php/LUMIN/article/view/568.