Górniewicz, L. and Nistri, P. (1999) “Topological essentiality and nonlinear boundary value control problems$^*$”, Topological Methods in Nonlinear Analysis, 13(1), pp. 53–72. Available at: https://apcz.umk.pl/TMNA/article/view/TMNA.1999.003 (Accessed: 22 July 2024).