Gruzdeva, T., A. Strekalovsky, A. Orlov, and O. Druzinina. “Nonsmooth Minimization Problems for the Difference of Two Convex Functions”. Numerical Methods and Programming (Vychislitel’nye Metody I Programmirovanie), vol. 12, no. 30, Oct. 2011, pp. 384-96, https://en.num-meth.ru/index.php/journal/article/view/474.