Caputo fractional systems with variable coefficients: Existence and stability results via Peano–Baker series. Letters in Nonlinear Analysis and its Applications, [S. l.], v. 4, n. 3, p. 137–157, 2026. DOI: 10.66147/lnaa.20264379. Disponível em: https://lettersinnonlinearanalysis.com/index.php/lnaa/article/view/79. Acesso em: 10 jul. 2026.