Savchin, V.M., and L.T. Huyen. “Nonpotentiality of a Diffusion System and the Construction of a Semi-Bounded Functional”. Bulletin of the Karaganda University. Mathematics Series 104, no. 4 (December 30, 2021): 118–129. Accessed July 3, 2025. https://mts.buketov.edu.kz/index.php/mathematics-vestnik/article/view/486.