Hefter, S. L. .; Goncharuk, A. B. . Linear Differential Equation With Inhomogeneity in the Form of a Formal Power Series over a Ring With Non-Archimedean Valuation. Ukr. Mat. Zhurn. 2022, 74 (11), 1463-1477. https://doi.org/10.37863/umzh.v74i11.7287.