Mozyrska, Dorota, Malgorzata Wyrwas, and Piotr Oziablo. “Digital PID Controllers With Fractional Variable Order Techniques and Two Discrete-Time Operator Variants”. Bulletin of the Polish Academy of Sciences Technical Sciences 73, no. 3 (April 30, 2025): e153831. Accessed August 14, 2026. https://wydawnictwo.pan.pl/index.php/bpasts/article/view/1655.