Nguen, T. K., and N. B. Fam. “On Continuous Dependence of Solutions of Linear Differential Equations on a Parameter in a Banach Space”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 51, no. 2, Feb. 1999, pp. 275–280, https://umj.imath.kiev.ua/index.php/umj/article/view/4610.