O. F. . Casas-Sánchez, J. . Galeano-Peñaloza, and J. J. . Rodríguez-Vega, “$p$-Adic Markov process and the problem of the first return over balls”, Ukr. Mat. Zhurn., vol. 73, no. 7, pp. 902–912, Jul. 2021, doi: 10.37863/umzh.v73i7.464.