Enclosure of solutions for elliptic boundary value problems with nonmonotone discontinuous nonlinearity Siegfried Carl — 1994 Banach Center Publications
Existence of extremal periodic solutions for quasilinear parabolic equations. Carl, Siegfried — 1997 Abstract and Applied Analysis
Sign-changing solutions for nonlinear elliptic problems depending on parameters. Carl, Siegfried; Motreanu, Dumitru — 2010 International Journal of Differential Equations
General comparison principle for variational-hemivariational inequalities. Carl, Siegfried; Winkert, Patrick — 2009 Journal of Inequalities and Applications [electronic only]
Nonsmooth and nonlocal differential equations in lattice-ordered Banach spaces. Carl, Siegfried; Heikkilä, S. — 2005 Boundary Value Problems [electronic only]
Existence of solutions for discontinuous functional equations and elliptic boundary-value problems. Carl, Siegfried; Heikkilä, Seppo — 2002 Electronic Journal of Differential Equations (EJDE) [electronic only]
Sign-changing and multiple solutions for the p -Laplacian. Carl, Siegfried; Perera, Kanishka — 2002 Abstract and Applied Analysis
Existence and comparison results for quasilinear evolution hemivariational inequalities. Carl, Siegfried; Le, Vy K.; Motreanu, Dumitru — 2004 Electronic Journal of Differential Equations (EJDE) [electronic only]