“…The literature is now very extensive and we refer to the comprehensive monograph [35]. We also mention the following works, some of which are directly related to this paper, others with a different emphasis (higher order equations, systems, nonlinear boundary conditions): superlinear parabolic equations [2, 6, 7, 14, 29-31, 33, 36, 38-41]; linear heat equation with nonlinear boundary conditions [10,15,20,27,28] ; superlinear parabolic equations with a potential [1,3,9,22,23,39]; superlinear parabolic systems [11-13, 26, 34]; superlinear fractional parabolic equations [18,19,21,32,37]; superlinear higher order parabolic equations [8,16,17,24,25].…”