HefterS. L., & GoncharukA. B. (2022). Linear differential equation with inhomogeneity in the form of a formal power series over a ring with non-Archimedean valuation. Ukrains’kyi Matematychnyi Zhurnal, 74(11), 1463 - 1477. https://doi.org/10.37863/umzh.v74i11.7287