LitovchenkoV. A. “Cauchy Problem for One Class of Pseudodifferential Systems With Entire Analytic Symbols”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, no. 9, Sept. 2006, pp. 1211–1233, https://umj.imath.kiev.ua/index.php/umj/article/view/3523.