Klimczak, L. (2015) “Two constant sign solutions for a nonhomogeneous Neumann boundary value problem”, Annales Universitatis Paedagogicae Cracoviensis Studia Mathematica, 14, pp. 47–62. Available at: https://studmath.uken.krakow.pl/article/view/13153 (Accessed: 31 October 2026).