BoichukО. A., and PokutnyiО. О. “Exponential Dichotomy and Bounded Solutions of Differential Equations in the Fréchet Space”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 12, Dec. 2014, pp. 1587-9, https://umj.imath.kiev.ua/index.php/umj/article/view/2248.