Degaichia, Hakima, and Salah Boulaaras. “A NEW PROOF FOR THE GLOBAL CONVERGENCE OF THE BFGS METHOD FOR NONCONVEX UNCONSTRAINED MINIMIZATION PROBLEMS”. Italian Journal of Pure and Applied Mathematics, vol. 37, July 2017, pp. 469-86, https://journals.uniurb.it/index.php/ijpam/article/view/6786.