Toparkus, H. (2014) “First-order systems of linear partial differential equations: normal forms, canonical systems, transform methods”, Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, 13, pp. 109–132. Available at: https://studmath.uken.krakow.pl/article/view/13194 (Accessed: 29 October 2026).