Dymkov, Michael P., and Siarhey M. Dymkou. “A Method for Relaxing State Constraints in Nonsmooth Optimal Control Problems”. Journal of the Belarusian State University. Mathematics and Informatics, no. 2, July 2022, pp. 107-14, https://doi.org/10.33581/2520-6508-2022-2-107-114.