1. Alt, H.W., Phillips, D.: A free boundary problem for semilinear elliptic equations. J. Reine Angew. Math. 368, 63–107 (1986)
2. Andersson, J.: Almost everywhere regularity for the free boundary of the normalized
$$p$$
p
-harmonic Obstacle problem
$$p>2$$
p
>
2
.
arXiv:1611.04397
3. Aris, R.: The mathematical theory of diffusion and reaction in permeable catalysts. In: Vol. I: The Theory of the Steady State. Clarendon Press, Oxford; Oxford University Press, London. XVI, p. 444 (1975)
4. Aris, R.: The Mathematical Theory of Diffusion and Reaction in Permeable Catalysts. In: Vol. II: Questions of Uniqueness, Stability, and Transient Behaviour. Clarendon Press, Oxford; Oxford University Press, London. XVI, p. 217 (1975)
5. Bandle, C., Sperb, R.P., Stakgold, I.: Diffusion and reaction with monotone kinetics. Nonlinear Anal. 8, 321–333 (1984)