Sasu, A. L., and B. Sasu. “Input-Output Conditions for Exponential Trichotomy of Dynamical Systems”. Rev. Anal. Numér. Théor. Approx., vol. 37, no. 2, Aug. 2008, pp. 209-15, https://ictp.acad.ro/jnaat/journal/article/view/2008-vol37-no2-art13.