Samia Challal (2021) “A Barrier Function for the Regularity of the Free Boundary in $div(a(x) \nabla u )=-(h(x)\gamma)_x$ with $h_x < 0$”, International Journal of Mathematics And its Applications, 9(4), pp. 35–43. Available at: http://ijmaa.in/index.php/ijmaa/article/view/26 (Accessed: 18 April 2024).